ELEMENTARY 
HOUSEHOLD CHEMISTRY 



THE MACMILLAN COMPANY 

NEW YORK • BOSTON • CHICAGO • DALLAS 
ATLANTA • SAN FRANCISCO 

MACMILLAN & CO., Limited 

LONDON • BOMBAY • CALCUTTA 
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THE MACMILLAN CO. OF CANADA, Ltd. 

TORONTO 



ELEMENTARY 
HOUSEHOLD CHEMISTRY 

AN INTRODUCTORY TEXTBOOK FOR 
STUDENTS OF HOME ECONOMICS 



BY 



JOHN FERGUSON SNELL 

PROFESSOR OF CHEMISTRY, MACDONALD COLLEGE 
MCGILL UNIVERSITY 






THE MACMILLAN COMPANY 
1914 

AH rights reserved 



^ 



<^4* 



Copyright, 1914, 
By THE MACMILLAN COMPANY. 



Set up and electrotyped. Published June, 1914. 



Nortoooti ^re0g 

J. S. Cushing Co. — Berwick & Smith Co. 

Norwood, Mass., U.S.A. 

JUN25I9I4 

©CI.A374577 

it 



PREFACE 

The recent development of courses of instruction in Home 
Economics in America has created a field for textbooks pre- 
pared to meet the special needs of this new class of students. 
The course in chemistry presented in this book is the outcome 
of several years' experience with a class of students, the ma- 
jority of whom have had no previous instruction in the science. 
The text has been written with the needs of such students 
primarily in mind, but the hope is entertained that, with suit- 
able omissions, it may also be found useful in the many insti- 
tutions in which the student of household chemistry approaches 
the subject after a preliminary training in general chemistry. 
The principle which has been kept constantly in mind is to 
introduce the applications of chemistry to household affairs as 
early and as often as possible and to present only such por- 
tions of the subject matter of theoretical chemistry as is 
essential to the comprehension of these applications. In this 
way the student's interest is enlisted and maintained — a most 
important consideration in the teaching of an applied science. 

The author's thanks are due to the many friends who have 
taken an interest in the preparation of this volume and more 
particularly to Professor John Bonsall Porter of McGill Uni- 
versity ; Mr. F. O. Farey, of the Robert W. Hunt Company, 
Montreal ; and Mr. Peter H. Walsh, Chemist of the Dominion 
Textile Company, Magog, Quebec, for suggestions in regard 
to the chapters on fuels, soaps, and textiles, respectively ; to 
Miss Katharine A. Fisher, Head of the Household Science 
Department, Macdonald College, for the table of weights of 
one cupful -of various food materials; and to Professor H. C. 
Sherman, of Columbia University, for numerous suggestions. 



VI PREFACE 

For permission to use illustrations the author desires to make 
acknowledgments to Misses Kinne and Cooley, authors of 
"Shelter and Clothing"; to Sir William Ramsay; to Pro- 
fessor R. H. Richards, and Mrs. W. O. Atwater ; to Messrs. 
Eimer and Amend, New York ; to the Niagara Electrochemi- 
cal Company ; and to the publishers. 

v J. F. SNELL. 

Macdonald College, 
January I, 1914. 



CONTENTS 



CHAPTER PAGE 

I. The Subject Matter of Chemistry. 1 

II. Decomposition and Combination . . . . 11 

III. Elements 18 

IV. Compounds 22 

V. Chemical Notation 26 

VI. The Atomic Theory 28 

VII. The Law of Definite Proportions .... 34 

VIII. Compounds of the Same Elements in Different 

Proportions 38 

IX. Combustion 41 

X. The Relation of Combustion to Heat ... 51 

XL Fuels 59 

XII. Fuels {Continued) 66 

XIII. Light and Illuminants 72 

XIV. Acids and Salts 82 

XV. Alkalies 91 

XVI. Bases and Basic Oxides 94 

XVII. Reactions of Acids with Bases and with Basic 

Oxides. Ionization 98 

XVIII. Metal Tarnishes 105 

XIX. Iron Rust 109 

XX. Strong and Weak Acids and Bases . . . 114 

XXI. Hydrolysis of Salts ....... 117 

XXII. Hard Water 121 

XXIII. Ammonia and the Ammonium Radicle . . . 127 

XXIV. Organic Radicles. Hydrocarbons and Alcohols 132 
XXV. Esters, Fats . .138' 

vii 



Vlll 



CONTENTS 



CHAPTER p AGE 

XXVI. Hydrolysis of Esters. Saponification . . 143 

XXVII. Commercial Soaps. . . ... . . 148 

XXVIII. Foreign Ingredients of Commercial Soaps . 151 

XXIX. Special Soaps and Scouring Powders . . 155 
XXX. Solution and Emulsification of Fats. The 

Cleaning of Fabrics 158 

XXXI. The General Composition of Foods . . . 162 

XXXII. The Carbohydrates. I 166 

XXXIII. The Carbohydrates. II . . . .173 

XXXIV. The Proteins. I 182 

XXXV. The Proteins. II . 188 

XXXVI. The Functions of Food 192 

XXXVII. The Digestion of Food 201 

XXXVIII. Foods of Vegetable Origin .... 207 

XXXIX. Foods of Animal Origin 213 

XL. Textile Fibers of Animal Origin. Wool and 

Silk 218 

XLI. Textile Fibers of Vegetable Origin. Cotton, 

Linen, and Artificial Silk . • . " . . 229 

XLII. Bleaching and Blueing 243 

XLIII. Dyeing 254 

Appendix A. — Tables of Composition of Foods . . 267 

Appendix B. — Reagents 288 

Appendix C. — The Metric System 294 



LIST OF PLATES 



OPPOSITE 
PAGE 



Ellen Henrietta Swallow (Mrs. Richards) 

Robert Boyle 

Jons Jakob Berzelius 

John Dalton . 

John Mayow . 

Joseph Priestley 

Antoine-Laurent Lavoisier 

Benjamin Thompson (Count Rumford) 

Joseph Black ..... 



Svante August Arrhenius 



Emil Fischer ..... 

Wilbur Olin Atwater 

The Atwater-Rosa Respiration Calorimeter 

The Atwater-Rosa-Benedict Respiration Calorimeter 

Textile Fibers, magnified ..... 






V 



i 

18 
26 
28 
42 
44 v 

46 v / 



52 
92 

98 

182 

192 

194 

196 

218 



IX 




Ellen Henrietta Swallow. 
Mrs. Robert Hallowell Richards. — 1< 



^2-IQII. 



Trained as a chemist, and engaged up to the time of her death in the teaching 
of chemistry, Mrs. Ellen H. Richards became one of the foremost leaders in the 
application of scientific principles to the management of the household. 



ELEMENTARY HOUSEHOLD 
CHEMISTRY 

CHAPTER I 
THE SUBJECT MATTER OF CHEMISTRY 

Chemistry is a science. The word science is derived from 
a Latin word, scire, meaning " to know." Science and knowl- 
edge are therefore closely related words. Science is knowl- 
edge. But the term science is applied only to such knowledge 
as is based upon careful and accurate observations and 
correct reasoning thereupon. A man might gain a rough 
knowledge of the distance between Montreal and New York 
by recalling that his grandfather had walked from the one 
city to the other in two weeks' time, and observing that he 
himself could walk twenty-five miles a day. Such knowl- 
edge would be unscientific. In contrast with it we have 
represented in our maps and geographical books the scientific 
statement of the distance between the two cities, based upon 
painstaking measurements or " surveys." 

In building up science we make much use of experiment ; 
that is, we arrange that the conditions under which we make 
our observations shall be as favorable as possible to accu- 
racy and to the drawing of correct conclusions. The man 
who wished to know the distance from New York to Montreal 
could obtain a more accurate estimate by making the journey 
himself on foot, taking care to maintain a uniform pace and 
to walk the same number of hours each day, than by relying 
upon his recollection of his grandfather's account of the time 



ELEMENTARY HOUSEHOLD CHEMISTRY 



required for the journey. The former would be an experi- 
mental determination of the distance. The professional sur- 
veyor's measurement is also an experimental one, but the 
conditions of observation are much more carefully controlled, 
and the correctness of the measurements is checked in many 
different ways, all depending upon experiments. 

Chemistry is only a branch of science. That is to say, it 
is the body of knowledge of a particular class of phenomena 
which the human race has been able to acquire by such 
carefully conducted experimental observations and such logi- 
cal deductions as we have referred to above. To understand 
what chemistry is, it is, therefore, necessary that we should 
get a clear conception of the kind of phenomena (changes) to 
which this science relates. And it is fitting that this clear 
conception should be gained through the use of experiments. 
In making experiments the student should bear in mind that 
the basis of all science is careful observation. She should 
therefore examine closely every material used and every stage 
of the experiment, so as to get as clear and full a knowledge 
as possible of what is going on under her eyes. 

A written record should be made of every experiment, 
and this record should always be in the fol- 
lowing order : 
i. What I did. 

2. What I observed (i.e. saw, smelled, 
tasted, heard, or felt). 

3. What I concluded from my observa- 
tions. 

The knowledge that one has to record an 
experiment always of itself conduces to more 
careful observation and reasoning. 




Fig. 1. — Bunsen 
burner. Ordi- 
nary form for 
use with coal 
gas. 



Experiment 1. The Bunsen Burner. — Un- 
screw and examine your gas burner. Make a 
sketch of the burner and indicate upon it where the gas enters 
and where the air enters. Learn how the supply of each is in- 



THE SUBJECT MATTER OF CHEMISTRY 



creased and diminished. Close the air holes. Turn on and light 
the gas and note the appearance of the flame. Hold a cold por- 
celain dish in the flame. Is soot deposited ? Gradually open the 
air holes and note the effect on the flame. Prac- 
tice lighting the burner with the air holes closed, 
and then regulating the supply of air and gas 
until you can readily obtain a good non-luminous 
(blue) flame. Determine whether such a flame 
deposits soot on the cold porcelain. 




Experiment 2. 

Materials: 

Magnesium ribbon in £-inch pieces. 

Platinum wire. 

Iron nail. 

Asbestos paper or light asbestos board, 2 
inches X 2 inch, previously ignited to de- 
stroy organic matter. 

Paper in pieces 2 inches X | inch. 

File. 

Crucible tongs or forceps. 

(1) Bring into the Bunsen (non-luminous) 

flame a piece of magnesium ribbon, held in a pair of forceps 
or crucible tongs. Describe what occurs. Examine the 

product. Is it magnesium ? 



Fig. 2. — Tirrill 
burner. A mod- 
ification of the 
Bunsen burner 
suitable for 
gasoline gas, 
as well as for 
coal gas. 




D 



Fig. 3. — Breaking a piece of glass 
tubing. Make a scratch on one 
side of the tubing with a single 
stroke of the file. Place the 
thumbs on the other side of the 
tubing, directly opposite the file 
mark. Grasp the tubing with 
the thumbs and press backwards 
towards the thumbs. 



In what respects does it dif- 
fer from magnesium ? 

(2) Bring a piece of platinum 
into the flame. Note the 
changes of color as it be- 
comes hot. Allow to cool. 
Is it still platinum ? 

In the same manner heat (3) 
an iron nail, (4) a piece of 
asbestos, (5) a piece of 



paper. 

Note appearance of each, (a) while it is in the flame, (b) after 

it has cooled again. 

Write in one column the names of those substances which are 

the same at the end of your experiment as at the beginning, and 

in another column those which have been changed into something 

different. The former suffered physical changes during the heat- 



4 ELEMENTARY HOUSEHOLD CHEMISTRY 

ing, the latter chemical changes. Note that iron will be classed 
differently, according as you consider (a) the outer surface or 
(b) the interior as disclosed by riling off the surface. 

Experiment 3.* 

Materials: 

An accumulator or any type of primary cell. 
A wire resistance. 
A mounted magnetic needle. 
Connect the two poles of a voltaic cell through a resistance. 
Bring a magnetic needle near the connecting wire. What occurs ? 
Break and remake the connection. Does the needle undergo a 
physical or a chemical change when brought near the wires ? 

Experiment 4. 

Materials : 

Glass tubing, about 6 mm. diameter. 1 
File. 
Cut off a piece of glass tubing about 15 cm. (6 in.) long. Heat 
the middle of the piece of tubing in the Bunsen flame, rotating it 

constantly. When it is quite soft, 
remove from flame, draw out to 
a small thread, and fuse off the 
thread in the flame, forming two 
small tubes closed at one end. 
Heat the closed end of each of 

Fig. 4. — Drawing out glass tubing. these tubes in the flame > rotating 

The glass is held above the inner constantly, and when quite soft, 

cone of the flame and is constantly remove from flame and blow into 

rotated until soft. Just before the end of the tub SQ as 

drawing, it is removed from the . . , ' 

fl ame to round out the glass. It may 

either be rounded off, forming 

simply a closed tube (Fig. 6) , or blown into a bulb, forming a matrass 

(Fig. 7). 




G 



Fig. 5. — Glass tubing drawn out. 

In what respects does the sealed tube differ from the original ? 
Is it still glass ? In what respects does hot glass differ from cold ? 

* All experiments marked by the asterisk are recommended for demonstration 
by the teacher rather than for performance by the individual student. 
1 See Tables of Metric System, p. 294. 



THE SUBJECT MATTER OF CHEMISTRY 



Are hot glass and cold glass different substances? 

suffer a physical or a chemical change during 
heating ? Does hot glass suffer phys- 
ical or chemical changes when drawn 
out, and when blown? 

Keep the matrass or sealed tube for 
use in a later experiment. 



Does glass 



m 







Experiment 5. 

Materials : 

Compressed yeast, | cake. 



KJ 



Fig. 7. — A 

matrass. 



Solid commercial grape sugar 
(" glucose " or " dextrose "), 
2.5 grams. 
Dissolve 2.5 grams glucose in 20 cc. water. Rub 
up a little yeast (| cake or 
less) with 5 cc. water. Add it 
to the glucose solution, and 



Fig. 6. — Glass 
tube closed at 
one end. The 
narrow thread 
of glass (Fig. 
5) is melted 
and drawn off. 
The end of the 
tube is then 
softened in the 
flame, and, by 
blowing, either 
rounded off or 
expanded into 
the bulb of a 
matrass (Fig. 
7). 



Fig. 9. — Glass loop 
for limewater films. 
This can be made 
from a piece of 
small (2 to 4 
millimeter) glass 
tubing by soften- 
ing in the flame, 
drawing out, and 
quickly turning 
the soft glass 
thread back upon 
itself. The loop 
should be about 
5 to 7 millimeters 
long and 2 to 3 
millimeters wide. 



allow to stand two or three 
hours in a test tube in a warm 
part of the laboratory. The 
effervescence (bubbling) ob- 
served is caused by the forma- 
tion of a gas (carbonic acid gas) 
which has the property of turning limewater 
milky. To test for the gas, dip a glass loop 
(Fig. 9) into limewater (calcium 
hydroxide) solution, and hold the 
film of liquid in the test tube 
above the glucose solution for 
about half a minute. Then look 
through the film towards the light. 
The test is obtained more promptly 
if the test tube has been loosely 
covered for a few minutes. 

The chemical change illustrated 
in this experiment occurs in the 
common fermentation of fruit juices (which con- 
tain glucose). Besides the carbonic acid, alco- 
hol is formed. While the carbonic acid gas 
escapes, the alcohol remains in the liquid and 
the fruit juices become wines, ciders, etc. 



Fig. S. — A 
test tube. 



6 ELEMENTARY HOUSEHOLD CHEMISTRY 

Experiment 6. 

Materials : 
Common salt. 

Silver nitrate — a solution and also a specimen of the solid 
substance. 

Dissolve the salt in water in a test tube. The silver nitrate 
reagent has been made similarly by dissolving solid silver nitrate 
in water. Note that both solutions are clear. Pour a little of 
the silver nitrate solution into the salt solution. The clouding 
which appears is due to the separation of innumerable minute 
particles of a substance (silver chloride) which does not dissolve 
in water. These particles are in the solid state. To verify 
this close the test tube with the thumb and shake vigorously, 
so as to combine the particles into larger ones. A solid forming in, 
and separating out from, a liquid is called a precipitate. In this 
experiment the substance silver chloride is formed as a precipitate 
when salt (sodium chloride) and silver nitrate solutions are mixed. 
At the same time a substance, called sodium nitrate, is also pro- 
duced, but this substance being soluble in water, like the original 
substances, does not make itself visible in the experiment. 

Experiment 7. 

Materials : 

Milk. 
Fold a filter and fit it in a glass funnel. Pour milk upon the 
filter. Does it pass through the filter unchanged? Add a few 





Fig. 10. — Folding a filter. Fig. ii. — Folding a filter. Fig. 12. — Folding 
First stage. Second stage. a filter. Third 

stage. 

drops of acetic acid to the milk, and again pour upon the filter. 
Has the acid caused a chemical change in the milk ? 



THE SUBJECT MATTER OF CHEMISTRY 




Experiment 8. 

Materials : 
Milk. 
Junket tablets or rennin solution. 

In a test tube surrounded by a beaker of water, heat milk to 
the temperature of the hand. Add 
a few drops of rennin solution or of 
an aqueous solution of junket tab- 
lets (which contain rennin) and 
mix. Allow to stand for 15 min- 
utes. Shake the test tube and pour 
the contents on a filter. Has a 
chemical change occurred in the 
milk? 

Experiment 9.* 

Materials : 

Potassium iodide crystals. 
Mercuric chloride crystals 
(Poison !) . 

Apparatus : Fig. 13. — A filter ready for use. 

Mortar and pestle. 
Rub together in the mortar a crystal of potassium iodide with 
one of mercuric chloride. What evidence appears that a new 
substance is formed? Actually two new substances are formed, 

but one of these is white like the potas- 
sium iodide and mercuric chloride. 

Experiment 10.* 

Dissolve a crystal of potassium iodide 
in water in a test tube. In another tube 
dissolve about an equal quantity of mer- 
curic chloride. Shaking and warming 
will hasten solution. Pour a little of the 
potassium iodide solution into a third 
test tube, and gradually add mercuric chloride solution to it. 
The red precipitate is the same red substance that was formed in 
Experiment 9. The white substance, referred to above as being 
formed at the same time, is in solution in the water. 

Note. Directions for making reagents called for in some of the experiments 
in this and other chapters will be found in Appendix B. 




Fig. 14. — Mortar and 
pestle. 



8 



ELEMENTARY HOUSEHOLD CHEMISTRY 



Experiment n.* 

Add the remainder of the potassium iodide solution to the test 
tube containing the red precipitate (Expt. 10). Does a chemical 

change occur? What is the 
evidence ? 



Experiment 12. 

Hold a cold, dry beaker, 
mouth downward, above a 
Bunsen flame for an instant. 
Note the deposition of dew — 
composed of minute droplets of 
water. Close the beaker with 
a watch glass, invert it, pour in 
a little limewater and shake. 
What gas was present in the 
beaker? (See Expt. 5.) 

Repeat this experiment, using 
an unlighted burner with the gas 
flowing. Is any dew deposited ? 
Is the gas which affects lime 
water present? What kind of 
change do you infer to be in- 
volved in the burning of gas? 




Fig. 15 

of 



— Collecting the products 
the burning of gas. 



EXERCISES 

1. Make a tabular summary of the results of Experiments 
3-12, putting the chemical changes into one column, the physical 
into another. 

2. Arrange the following changes in their proper columns as 
(a) chemical or (b) physical : 

(a) Breaking stone. 

(6) Passing an electric current through a copper wire. 

(c) Making horseshoes from bar iron. 

(d) Making wine from fruit juice. 

(e) Burning wood. 

(/) Milling wheat, i.e. grinding it and separating the flour from 

the bran. 
(g) Ironing linen. 
(h) Scorching linen. 



THE SUBJECT MATTER OF CHEMISTRY 9 

(i) Manufacturing glass from sand, soda, and lime. 

(j) The rusting of iron. 

(k) The growing of a tree. 

(/) The assimilation of food by an animal. 

All the changes which substances undergo in the pro- 
cesses of nature and of the arts may be divided into trie two 
classes illustrated by the above experiments, viz. : 

1. Physical changes, in which no new substance is formed. 
Changes in state of motion, such as that involved in throw- 
ing or catching a ball, are purely physical. So also are 
changes in form, such as are produced by cutting, grinding, 
or hammering. Changes in temperature and changes in 
electrical condition may bring about chemical changes, but 
they are not in themselves chemical. 

2. Chemical changes, in which one or more new sub- 
stances are formed. We recognize new substances by 
observing such physical properties as color, physical state 
(solid, liquid, or gaseous), density (weight of a given volume, 
" heaviness "), solubility in water or in other solvents, etc. 
In some instances it is difficult to decide whether a new 
substance has been formed or not. But in many others, 
as we have seen in the experiments, the product of the 
change is readily recognized as a new substance. 

Chemistry is the science which treats of those changes 
or " reactions " in which new substances are formed. 

Chemical changes seldom, if ever, occur without the accom- 
paniment of physical changes. In Experiment 2, for example, 
not only is a new substance formed in place of the magne- 
sium, but heat and light are given out. Again, the heat 
evolved produces an upward current in the air, and some of 
the white, solid product of the chemical change is carried up 
as a smoke. There are thus a number of physical changes 
occurring concomitantly with the chemical change. In 
studying chemical changes we cannot ignore these concomi- 
tant physical changes, but we direct our attention partic- 



IO ELEMENTARY HOUSEHOLD CHEMISTRY 

ularly to the question whether new substances have been 
produced, and, if so, what those new substances are. 

It must not be thought, however, that chemical changes 
are the only objects of study in the science of Chemistry. 
The science includes also the study of the properties of sub- 
stances and of their " composition," a term which will be 
understood when the next three chapters have been read. 



CHAPTER n 

DECOMPOSITION AND COMBINATION 

The following experiments illustrate chemical changes of 
two classes. The chief point to be studied in each experi- 
ment is the alteration in the number of substances present. 

Experiment 13. 

Materials : 

Mercuric oxide (best the red modification prepared by igni- 
tion) . 
Matrass or glass tube closed at one end, prepared in Experi- 
ment 4. 
Splints of pine or other soft wood. 
Heat mercuric oxide in a matrass or glass tube closed at one end. 
Test the escaping gas with a glowing splint. Note what collects 
on the inner surface of the tube. How many substances were put 
into the matrass? How many new substances were formed? 
Is this a chemical or a physical change ? 
The gas which affects the splint is called oxygen. 

Experiment 14. 

Materials : 

Potassium chlorate. 
Splints. 

Heat potassium chlorate in a test tube until bubbling ceases. 
Apply a glowing splint to the gas escaping during the bubbling. 
Determine whether the sub- 
stance left in the tube is potas- 
sium chlorate or not. For this 
purpose not only may the effect 
of heat on this residual sub- 
stance be compared with that on 
, , . . 1 , , Fig. 10. — A test tube holder. 

the original potassium chlorate, 

but also a portion of each may be dissolved separately in water 
and treated with silver nitrate solution. 

11 




12 



ELEMENTARY HOUSEHOLD CHEMISTRY 



In the main experiment how many substances were put into the 
tube to be heated ? How many new substances were found to be 
formed ? 



\ 



Experiment 15. 

Heat a little sugar (about 0.5 gram) in a test tube. Note what 

escapes from the tube and 
what is left in it. Test the 
escaping gas with blue lit- 
mus paper. How many 
substances were put into 
the tube? Were new sub- 
stances formed? How 
many were detected? 

Experiment 16.* 

Materials : 

Sulphuric acid solution, 
about 10 per cent. 
Apparatus : 

Hofmann's electrolysis 
apparatus (Fig. 18) 
or the simpler ap- 
paratus represented 
in Figure 17. 
3 accumulators in 
series (or other ap- 
propriate source of 
direct current). 
With the Hofmann ap- 
paratus full of the dilute 
sulphuric acid solution up 
to the bottom of the reser- 
voir (or with the test tubes 
of the simplified apparatus 
full of the acid and inverted 
in the beaker of acid) con- 
nect the battery to the bind- 
ing posts and allow the current to pass until a considerable quantity 
of gas has collected in each branch of the apparatus. Note that 
about twice as much gas collects in one branch of the apparatus 
as in the other. Invert a small test tube over one of the outlet 




Fig. 



17. — A simple apparatus for 
the electrolysis of water. 



DECOMPOSITION AND COMBINATION 



13 



tips, open the cock, and allow the gas to escape into the test 
tube. Cover the tube with the thumb, invert, and immediately 
apply a flaming splint. Make the same test upon the gas from 
the other limb of the apparatus. Also test each with a splint 
with a glowing, but not flaming, end. Compare the behavior of 
the two gases. One of these gases is the substance already 
met with in Experiments 13 and 14. What 
is its name ? The other is hydrogen. Which 
of the gases is obtained in the larger quan- 
tity? Careful experiments have shown that 
none of the sulphuric acid is used up in this 
experiment. Indeed, several other substances 
can be substituted for the sulphuric acid with- 
out altering the result. The amount of water 
in the apparatus is, however, a little less after 
the experiment than before. The diminution 
of the quantity of water is not visible, unless 
the current has been passed for some hours. 
But it has been found by accurate measure- 
ment that the water lost weighs exactly the 
same as the sum of the weights of the hydro- 
gen and oxygen produced. The use of the 
sulphuric acid is to make the water a better 
conductor of electricity. Pure water con- 
ducts electricity so badly that, using it, we 
should require years to obtain as much gas 
as we do in a few minutes with the mixture 
of sulphuric acid and water. 

If the hydrogen and oxygen produced in 
the electrolysis of water are both collected 
and mixed and set on fire, an explosion takes 
place, and if the experiment is conducted in 
a closed apparatus strong enough to stand 
the shock of the explosion, there is found in the apparatus after 
the explosion a quantity of water weighing just the same as the 
hydrogen and oxygen, and therefore just the same as the water 
which was destroyed by the electrolysis that produced the hydro- 
gen and oxygen. 

Experiment 17.* 

In a hard-glass test tube fitted with a cork and bent delivery 
tube and supported in a clamp on a ring stand heat a piece of 




Fig. 18. — Hofmanris 
apparatus for the elec- 
trolysis of water. 



14 ELEMENTARY HOUSEHOLD CHEMISTRY 

marble weighing from 2 to 5 grams. A large Bunsen or a Teclu 
or Meker burner should be used. Immerse the lower end of the 
delivery tube in limewater, contained in a small test tube. Con- 
tinue to heat for several minutes and note the continued slow 
evolution of gas and the effect of the gas on limewater. 

To hasten the action transfer to a porcelain crucible the marble 
remaining in the test tube and heat in the flame of a blast lamp 
for 15 to 30 minutes. Allow to cool and examine the residue. Add 
to it as much warm water as it will absorb and allow it to stand 
a few minutes. Add more water to the product and test the water 
with litmus paper. 

The material of which marble consists is known in chemistry 
as calcium carbonate. The gas, which it evolves on heating and 
which affects the limewater, is called carbon dioxide, and the 
residue left in the crucible after all the carbon dioxide has been 
driven out is quicklime or calcium oxide. Quicklime is commonly 
made from limestone, a less pure calcium carbonate than marble. 
Quicklime and water react to form slaked (or slacked) lime, and 
slaked lime dissolves slightly in water, yielding limewater. 

The student will have observed that in each of the above 
experiments (Nos. 13-17) one substance is converted into 
two or more new substances. Chemical change of this type 
is called decomposition. Thus we say that the red solid, 
mercuric oxide, is decomposed by heating into the metallic 
liquid, mercury, and the colorless gas, oxygen; and that water 
under the influence of an electric current decomposes into 
the two gases, hydrogen and oxygen. A great many sub- 
stances are decomposed by heating, and some of them, 
like the sugar in Experiment 15, give a large number of de- 
composition products. A great many also are decomposed 
by the electric current, and a special name, electrolysis, is 
applied to decomposition so effected. The decomposition 
products, we say, are simpler substances than those from 
which they are made. Thus, mercury and oxygen are 
simpler substances than mercuric oxide ; and potassium 
chloride (the white residue in Expt. 14) and oxygen are 
simpler substances than potassium chlorate. 



DECOMPOSITION AND COMBINATION 15 

In many instances the decomposition products can be 
readily recombined into the original substance. For instance, 
the hydrogen and oxygen obtained from water in Experiment 
16 can be recombined into water by simply mixing the 
gases and setting the mixture on fire. We are therefore 
justified in regarding the more complex substances as com- 
pounds of the simpler. Thus we say that mercuric oxide 
is composed of mercury and oxygen, or that it is a compound 
of the simpler substances, mercury and oxygen — although 
it does not in the least resemble either of these simpler 
substances ; and that water is a compound of hydrogen and 
oxygen (p. 13). When water is put upon hard lumps of 
quicklime the two substances combine, forming the powdery 
substance which we call slaked lime. (See Expt. 50, p. 
96.) 

We commonly speak of the decay of dead animal and 
vegetable matter as "decomposition." The chemical changes 
involved in such decay are much more complex than any 
of those we have studied in our experiments. Every animal 
or vegetable organism comprises a great many different 
substances. Even the parts our eyes readily recognize as 
different — such as bone, blood, muscular tissue (flesh), 
and fat — are generally mixtures of a number of different 
substances. And very commonly substances outside of the 
organisms, particularly water and air, are involved in the 
process of decay. Nevertheless, since such decay does 
result for the most part in the production of simpler sub- 
stances than those originally present in the decaying organ- 
ism, the word decomposition as applied to decay has a signifi- 
cation closely allied to our definition of the term. 

Chemical change which results in the formation of one 
substance from two or more is called combination. Com- 
bination has already been illustrated in the instance of 
hydrogen and oxygen. The following experiments furnish 
further illustrations of this class of chemical action. 



i6 



ELEMENTARY HOUSEHOLD CHEMISTRY 



Experiment 18. 

Materials : 
Roll sulphur. 
Copper foil, i inch X i inch. 

Heat a little roll sulphur to boiling in a test tube. While the 
sulphur is actively boiling, drop in a piece of copper foil. Note 
what occurs. The great majority of chemical changes are accom- 
panied by the evolution of more or less heat. In some, the heat 
is so great as to make the solid substances involved in the change 
give out light. Many of the chemical reactions which produce 
great quantities of heat belong to the class we are now considering, 
viz. combinations. (See Expt. 19.) 




m) ) Wrr^rvl 



□ED 




Fig. 19. — Burning carbon (charcoal) in a current of oxygen. The oxygen is 
generated in the flask by heating potassium chlorate. By bubbling through 
30 per cent potassium hydroxide in the first wash bottle, it is freed from 
any carbon dioxide it may contain. It then passes through the heated 
glass tube containing the charcoal, and finally through the second wash 
bottle, which contains limewater. (Experiment iq.) 

Examine the product formed from the copper, comparing it with 
the original copper and sulphur as regards color, cohesion, etc. 
(Ordinarily there will be a considerable quantity of unchanged 
sulphur left in the test tube, but this is readily distinguished from 
the new substance, which takes more or less nearly the form of 
the piece of copper used.) In this experiment how many sub- 
stances entered into action and how many new ones were formed ? 



DECOMPOSITION AND COMBINATION 



17 



Experiment 19.* 

Materials : 

Lumps of charcoal, thoroughly dried by heating. 

Apparatus: 

Oxygen generator, or cylinder of compressed oxygen provided 
with a soda-lime tube or with a wash bottle containing a 
30 per cent solution of potassium hydroxide. 
Small combustion furnace (with 4-10 burners). 
Hard-glass tubing. 
Glass and rubber tubing for connections. 

Place a few lumps of dried charcoal in a hard-glass tube in a 
small combustion furnace. Provide the tubes with corks and 
connect one end with the oxygen gener- 
ator, the other with a delivery tube. 
Pass oxygen through the apparatus to 
expel the air. Immerse the end of the 
delivery tube in limewater and continue 
to pass pure oxygen through the appara- 
tus. Is the limewater affected by the 
pure oxygen? 

Heat the hard-glass tube gently at 
first, then gradually raise the heat to 
redness. Pass a very slow current of 
oxygen over the heated carbon into the 
limewater. What occurs? What gas 
has been formed? 

If the experiment is continued long 
enough, the charcoal will disappear, 
leaving only a small quantity of white 
or gray ash. Except for this ash, 
charcoal consists entirely of a substance 
called carbon. This substance, when 
raised to a sufficiently high temperature, 
combines with oxygen. What sub- 
stance is the product of this combina- 
tion? 

Air contains oxygen, and exactly the 
same chemical action takes place when charcoal burns in a draft of 
air as when it burns in pure oxygen. Is any heat produced in 
this combination? What practical use is made of this chemical 
change ? 




Fig. 20. — Oxygen generator 
using fused sodium peroxide 
and water. Oxygen pre- 
pared in this way contains 
no carbon dioxide. When 
this style of generator is 
employed limewater may 
be used in both the wash 
bottles, or the first wash 
bottle may be omitted en- 
tirely. 



CHAPTER III 

x ELEMENTS 

Water, which is one of the decomposition products of 
sugar (see Expt. 15), may, as we have seen in Experiment 16, 
be itself decomposed into hydrogen and oxygen. In Experi- 
ment 14 one of the products obtained in the decomposition 
of potassium chlorate is potassium chloride, a white solid. 
If this substance is highly heated, it melts, and if an electric 
current is passed through the molten mass, decomposition 
occurs, the products being a soft metal, called potassium, 
and a greenish yellow gas, called chlorine. 

While, therefore, water is a simpler substance than sugar, 
it is less simple than hydrogen and oxygen ; and while 
potassium chloride is a simpler substance than potassium 
chlorate, it is evidently less simple than potassium and 
chlorine. 

When limestone is heated in a limekiln, quicklime and 
carbon dioxide (carbonic acid gas) are produced. (See Expt. 
17.) But carbon dioxide, as we have seen (Expt. 19), is 
composed of the simpler substances, carbon and oxygen. 
Similarly, quicklime is a compound of a metal called calcium 
and the gas oxygen. 

We see, then, that the products of some decompositions 
can in their turn undergo decomposition. However, there 
are a number of substances which it has not been found 
possible to decompose. Among these are hydrogen, oxygen, 
potassium, chlorine, calcium, mercury, and carbon. 

Substances which we cannot decompose are known as elements. 
This is the only sense in which the word element is used in 
chemistry. When we speak, as we commonly do, of wind 

18 




The Hon. Robert Boyle. — 1626-1691. 

The great English chemist who originated the modern conception of 
elements. Born in Ireland, a son of the first Earl of Cork, Boyle was 
educated in England and spent most of his life at Stalbrige, Dorsetshire. 
He was a member of the " Invisible College," an association of men de- 
voted to the new experimental philosophy, and of the Royal Society, into 
which the Invisible College developed (1663). Boyle's predecessors had 
studied chemistry with a view to its applications to medicine or to the 
transformation of the baser metals into gold. He studied it with the 
single purpose of discovering the truth. 



.: 



ELEMENTS 1 9 

and rain as " the elements," or, as the ancients did, of fire, 
air, water, and earth as the elements, we are not speaking 
scientifically, but rather poetically. It is not even permis- 
sible to speak of quicklime and carbon dioxide as elements 
of limestone, though we may call them the constituents of 
limestone. The elements of limestone are calcium, carbon, 
and oxygen. In science every word has a very definite 
meaning, and words of slightly different signification may 
not be interchanged, as they frequently are in common 
speech. 

Recent investigation growing out of the discovery of radio- 
activity has shown that some of the elements, such as uranium, 
thorium, and radium, gradually change into other elements. No 
means has yet been found to cause, or prevent, or in any way to 
control, such changes, which are nevertheless going on at an entirely 
definite rate. The distinction between this kind of change and 
decomposition proper can scarcely be made clear without reference 
to the atomic theory, which will be outlined later. (See Chapter 
VI.) 

At present (1913) eighty-three substances are officially 
recognized as elements by an international committee of the 
leading chemical societies of the world. Some of these are 
familiar substances like iron, gold, silver, copper, carbon 
(charcoal), and sulphur; others are substances rarely heard 
of in ordinary speech. A list of these eighty-three sub- 
stances will be found at the end of Chapter VI. In addition 
to these there are a few other rare substances which in all 
probability are also elements, but which have not been 
investigated thoroughly enough to secure official recognition. 

Eleven of the recognized elements are gases. Of these the most 
important are oxygen, hydrogen, nitrogen, and chlorine. Two 
elements are liquids, one of which, mercury, is familiar from its 
use in thermometers and barometers, while the other, bromine, 
is a disagreeable-smelling, red, fuming substance. Of the seventy 
solid elements several examples are given in the preceding para- 
graph. 



20 ELEMENTARY HOUSEHOLD CHEMISTRY 

Gas, liquid, and solid are the three physical states of matter 
(a general term for all substances). The elements which 
under ordinary conditions are gases can be changed into 
liquids and solids by more or less intense cooling and com- 
pression. Many of those which under ordinary conditions 
are solids can easily be melted by heating, e.g. tin, lead, 
sulphur. They thus become liquids. By further heating 
many of them have been converted into gases, e.g. sodium, 
sulphur, mercury, bromine. There can be little doubt, 
then, that under suitable conditions every element can be 
made to exist in all three physical states, and when we speak 
of oxygen as a gas or of sulphur as a solid, it is understood 
that we are referring to the ordinary temperature of a room, 
about 2o° C. (68° F.j. 

Metals and Non-Metals 

The great majority of the solid elements, and one of the 
two liquids (mercury), are classed as metals. Metals 
have certain chemical, and the following physical, 
characteristics: (i) A bright luster, when polished; {2) good 
conducting power for heat; (3) good conducting power for 
electricity. Among the elements of this class are the familiar 
metals, iron, tin, zinc, copper, silver, gold, etc., and other 
important but less familiar substances, such as sodium, 
potassium, calcium, and radium. Among the non-metals 
are such solids as carbon (which exists in the three forms of 
charcoal, graphite, and diamond), sulphur, phosphorus, and 
iodine; the evil-smelling red liquid, bromine; and all the 
gaseous elements. 

Experiment 20. 

Examine samples of the following elements and classify them 
as metals and non-metals : iron, platinum, sulphur, phosphorus, 
gold, silver, copper, carbon (charcoal), iodine, zinc, calcium, 
magnesium, sodium, potassium, mercury, bromine. 



ELEMENTS 2 1 

Experiment 21. 

Materials : 

Covered jars of chlorine, oxygen, hydrogen, and nitrogen. 

Examine specimens of the four common gaseous elements. 
Remove the cover of each jar slightly, and waft a very little of the 
gas towards the nose. Be especially careful not to take a full breath 
of the chlorine. Which of these four gases is readily distinguished 
by its color and odor? Note the different effects of the other 
three upon a burning splint of wood. 



CHAPTER IV 
COMPOUNDS 

A ^ The products of chemical combination of the elements 
are called compounds. Thus, water is a compound of oxygen 
and hydrogen; salt is a compound of sodium (a metal) and 
chlorine (a yellow gas) ; saltpeter is a compound of the metal 
potassium with the gaseous elements nitrogen and oxygen; 
and sugar is a compound of carbon with hydrogen and oxygen. 
A compound is to be clearly distinguished from a mixture. 
Sulphur and iron can be mixed by grinding the two together 
in a mortar. In the mixture each of the two elements 
retains its individual characteristics. The iron is still 
attracted by a magnet. Carbon disulphide dissolves out 
the sulphur, leaving the iron undissolved; hydrochloric 
acid dissolves the iron, leaving the sulphur untouched. But 
when iron arid sulphur are heated together, a new substance, 
iron sulphide, is formed, which is entirely different from 
either of its elements. It is not attracted by the magnet ; 
carbon disulphide dissolves out nothing from it, while it 
dissolves completely in hydrochloric acid, liberating a gas 
different from that produced by the action of the acid on 
iron. 

Experiment 22.* 

Materials : 

Iron powder or fine filings. 

Sulphur. 

Carbon disulphide. 

Iron sulphide. 
A pparatus : 

Mortar and pestle. 

Magnet. 

22 



COMPOUNDS 



23 



Grind together in a mortar about 2 grams each of sulphur and 

iron. Divide the mixture into two portions. Place one portion 

in a test tube and heat to redness. Do you observe any evidence 

of chemical action? Allow the 

test tube to cool, break it, and 

examine the contents. Grind 

these and compare with the 

unheated portion. Make the 

following tests upon each of 

these two powders, comparing Fig. 21.— Softening glass tubing in order 

to bend it. To produce a long, narrow, 
yellow flame, provide the Bunsen 
burner with a " wing top," and close 
the air holes at the base of the burner. 
Hold the glass above the dark inner 
cone of the flame (which is cool) 
and keep it rotating until soft enough 
to bend. 




the results : 

(a) Pass a magnet through 
the powder. If both powders 
are attracted by the magnet, 
shake the magnet and see 
whether there is in either case 
any evidence of a separation of 
the iron and sulphur from each other ; also which powder is more 
strongly attracted. 

(b) Shake a little of the powder in a test tube with carbon 
disulphide. Pour off the carbon disulphide through a filter on 
to a watch glass and set aside in a warm place but not near a flame. 

When the carbon disulphide has 
evaporated, is a residue left in either 
watch glass? What is this residue? 
(c) Treat a portion of the powder 
in a test tube with dilute hydro- 
chloric acid. Note the odors. Also 
treat a portion of the iron powder 
with dilute hydrochloric acid. In 
this test, which powder gives an odor 
identical with that given by the iron 
itself? If the differences between 
the mixture of iron and sulphur and 
the compound prepared in this ex- 
periment are not sufficiently marked 
(as may happen if some of the iron and sulphur have not reacted 
together), the above comparisons may also be made between the 
mixture and a portion of the sample of iron sulphide supplied. 

Refer to your notes on Experiment 18 (p. 16) and describe the 
compound of copper and sulphur, noting differences between that 
compound and its elements. 




Fig. 22. — Bending glass tubing. 
Remove the softened glass 
from the flame and immedi- 
ately bend it to the desired 
angle. 



24 ELEMENTARY HOUSEHOLD CHEMISTRY 

Air is a mixture of the two gases, nitrogen and oxygen. 
A similar mixture can be made of hydrogen and oxygen. 
This latter mixture is, of course, not air, but it is a clear, 
colorless gas looking exactly like air, and also like the unmixed 
elements — hydrogen and oxygen. But when oxygen and 
hydrogen combine, the resulting compound, water, is a liquid, 
entirely unlike the elements from which and of which it 
is formed. The compound (water) can be produced by set- 
ting fire to the gaseous mixture of oxygen and hydrogen. 

Further Discussion of the Subject Matter of Chemistry 

Having learned that all substances can be resolved into 
a limited number of elements, we are prepared to add some- 
thing to the definition of the subject matter of chemistry 
made in Chapter I. In studying chemistry we examine 
bodies or objects with special reference to their composition. 
We endeavor to find out what substances the objects under 
.consideration are made of, what elements they contain, and 
whether these elements are present in the free state or com- 
bined into compounds. Chemical analysis is the art of 
finding out the composition of bodies. Chemistry is the 
science which treats of the composition of bodies. This 
is, of course, not intended as a complete definition of chem- 
istry, for the science investigates not only what substances 
are present in a given body, but also under what conditions 
these substances are transformed into other substances by 
rearrangement of the elements. 

Nomenclature of Compounds 

The number of chemical compounds of the eighty-odd 
elements is enormous. To provide systematic names for 
them all many devices are required, but only two of the 
fundamental principles of nomenclature require consideration 
at this point. 



COMPOUNDS 25 

1. The suffix -ide implies that no elements are present, 
other than those mentioned in the name of the compound. 
Thus, sodium chloride (common salt) contains no elements 
but sodium and chlorine; ferrous sulphide, none but iron 
and sulphur; calcium oxide, none but calcium and oxygen, 
etc. 

2. The suffix -ate (also the less common one -ite) 
implies that, in addition to the elements named, the com- 
pound contains oxygen. Thus, potassium nitrate (saltpeter) 
contains potassium, nitrogen, and oxygen; potassium chlorate 
is a compound of potassium, chlorine, and oxygen; and 
magnesium sulphate (Epsom salt) is composed of magnesium, 
sulphur, and oxygen. 

EXERCISE 

What elements do the following compounds contain : (1) Calcium 
oxide, (2) Magnesium nitrate, (3) Silver chloride, (4) Hydrogen 
sulphide, (5) Sodium sulphate, (6) Gold chloride, (7) Potassium 
iodide, (8) Magnesium iodate, (9) Sodium sulphite, (10) Calcium 
phosphate ? 



CHAPTER V 
CHEMICAL NOTATION 

Chemists represent each element by a symbol, usually 
the initial letter of the Latin name, which in most cases is 
identical with the initial letter of the English name. Ex- 
amples : 

Oxygen, O Nitrogen, N 

Hydrogen, H Carbon, C 

Iron (Ferrum), Fe Potassium (Kalium), K 
Tin (Stannum), Sn 

Where the names of two or more elements have the same 
initial the symbols of all but one have a second characteristic 
letter added to the initial. Thus : 

Boron, B Sulphur, S 

Barium, Ba Silicon, Si 

Bromine, Br Strontium, Sr 

Carbon, C Silver (Argentum), Ag 

Chlorine, CI Sodium (Natrium), Na 

Cobalt, Co 
Chromium, Cr 
Copper (Cuprum), Cu 

Compounds are represented by formulas made up of the 
symbols of the composing elements. Thus: Ferrous sul- 
phide, FeS ; Calcium oxide, CaO. To the chemist the 
formula signifies not merely the qualitative but also the 
quantitative composition of the compound — not only what 
elements it contains, but in what proportions they are present. 
For this purpose the formulas of most compounds contain 
some figures in addition to the symbols of their elements. 
Thus: Water, H 2 ; Sulphuric acid, H 2 S0 4 ; Potassium 

26 




Baron Jons Jakob Berzelius. — 1779-1848. 

The Swedish chemist who originated our modern system of chemical nota- 
tion. Berzelius, the most influential chemist of the early part of the nineteenth 
century, excelled as an experimenter, as a philosopher, and as a teacher. He 
discovered several of the elements and determined the atomic (or " combining ") 
weights of those previously known. 



CHEMICAL NOTATION 27 

chlorate, KCIO3 ; Carbon monoxide, CO, but Carbon diox- 
ide, C0 2 ; Cane sugar, C12H22O11 ; etc. 

Chemical changes or reactions, as they are often called, 
are represented by equations, one side of which is made up 
of the formulas of the reacting substances (together with 
certain figures), the other side of the formulas of the products 
of the reaction. Thus : 

2 H 2 + 2 = 2 H 2 0, or 2 H 2 + 2 -> 2 H 2 
signifies that hydrogen and oxygen unite, forming water; 

2 KCIO3 = 2 KC1 + 3 2 
that potassium chlorate decomposes into potassium chloride 

and oxygen; 

Fe + S = FeS 

that iron and sulphur combine to form ferrous sulphide; and 

AgN0 3 + NaCl = AgCl + NaN0 3 

that silver nitrate and sodium chloride (common salt) react, 

forming silver chloride and sodium nitrate. 

The table on p. 33 gives the names and symbols of all 
the eighty-three substances accepted as elements in the 
year 1913 by the International Committee of Chemists 
referred to above (p. 19). 

The twenty-six elements of chief interest to the house- 
keeper are given also in the table on inside of back cover. 

EXERCISE 

Referring to the table at the end of Chapter VI for the 
interpretation of the symbols, write names for the compounds 
represented by the following formulas : 

(1) FeS, (2) K 2 S, (3) Na 2 C0 3 , (4) KN0 3 , (5) Ca(N0 3 ) 2 , (6)CaS0 4 , 
(7) MgCl 2 , (8) FeP0 4 , (9) KCIO3, (10) HgO. 

Write formulas, omitting figures, for the compounds 
whose names follow : 

(1) Silver iodide, (2) Sodium nitrate, (3) Potassium iodate, 
(4) Magnesium nitride, (5) Calcium sulphate. 



CHAPTER VI 
x THE ATOMIC THEORY 

Our chemical formulas are an outgrowth of the atomic 
theory, originated by John Dalton, an English teacher 
and chemist, about 1803. According to Dalton's theory 
all substances are made up of minute particles, which (in 
the modern terminology of the theory) are called molecules 
(diminutive from Latin, moles, mass). The smallest visible 
particle of any substance contains millions of such mole- 
cules. 

Lord Kelvin estimated that if a drop of water were magnified 
to the size of the earth, the molecules would appear larger than 
small shot but smaller than cricket balls. Even invisible gases 
are regarded as composed of molecules, and it has been estimated 
that one cubic centimeter of gas (measured at ordinary tempera- 
ture and pressure) contains approximately thirty million million 
million molecules. 

The molecules of each pure substance (whether element or 
compound) are conceived of as being exactly like one another 
but different from those of every other substance. The 
difference recognized is a difference of mass, and weighing is 
our most familiar way of comparing masses. All the mole- 
cules of any given substance, such as water, are equal in 
weight, but the weight of a water molecule is different from 
that of an alcohol molecule. 

The molecules of a substance cannot be in any way sub- 
divided without destroying the substance — not annihilating 
it, but converting it into other substances. In chemical 
decompositions the molecules of the original substance are 
split up into the smaller molecules of the decomposition 

28 











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psur 





John Dalton. — 1 766-1844. 

Dalton originated the modern atomic theory and roughly determined 
the atomic weights of several elements. 



THE ATOMIC THEORY 29 

products. Thus, when calcium carbonate (limestone or chalk) 
decomposes into calcium oxide (quicklime) and carbon 
dioxide (see Expt. 17, p. 13), we conceive that each mole- 
cule of the calcium carbonate has split up into two smaller 
molecules — one the molecule of calcium oxide, the other 
the molecule of carbon dioxide. 

The molecules of compounds are conceived to be made 
up of particles of the constituent elements of the compounds. 
Such particles of the elements are known as atoms. Thus, 
the molecule of calcium oxide would contain at least one atom 
of calcium and one atom of oxygen. 

The symbols of the elements are used to represent the 
atoms. The formula, CaO, stands for a molecule of calcium 
oxide, composed of one atom of the element calcium and one 
atom of the element oxygen. Similarly, the formula, KC1, 
stands for a molecule of the compound potassium chloride, 
consisting of one atom of the element potassium (K) and one 
atom of the element chlorine (CI). 

The formula, CO2, represents a molecule of carbon dioxide, 
consisting of one atom of carbon united to two atoms of 
oxygen ; the formula, H 2 0, a molecule of water, composed of 
two atoms of hydrogen united to one atom of oxygen ; and 
the formula, KCIO3, a molecule of potassium chlorate con- 
taining one atom each of potassium and chlorine and three 
atoms of oxygen. The chemists' reasons for regarding a 
molecule of carbon dioxide as containing two atoms of oxygen 
rather than one need not concern us here — though we may 
note that there is another compound of carbon and oxygen, 
called carbon monoxide, whose molecule is regarded as com- 
posed of one atom of each of the two elements. This sub- 
stance, carbon monoxide, is represented by the formula, 
CO. 

The molecules of any substance — for instance the cal- 
cium carbonate molecules in a piece of limestone — are con- 
ceived to be in motion. Physical changes may often be 



30 ELEMENTARY HOUSEHOLD CHEMISTRY 

accounted for by changes in the arrangement of the mole- 
cules with respect to one another or in the rate or manner of 
motion of the molecules. Heating, for example, is believed 
to make the molecules move faster. But any change which 
results in a disruption of the molecule or a rearrangement of 
the atoms so as to form new molecules is a chemical change. 
In calcium carbonate such a disruption takes place when the 
temperature has become sufficiently high. According to 
the theory, the molecules have then acquired so rapid a 
motion that they break asunder into molecules of calcium 
oxide and molecules of carbon dioxide. 

In the electrolysis of water the atoms of hydrogen and 
oxygen composing the molecule of water separate from one 
another. The hydrogen atoms set free at the one electrode 
unite in pairs to form hydrogen molecules, H 2 ; and the oxygen 
atoms set free at the other electrode likewise unite in pairs, 
forming oxygen molecules, O2. Two molecules of water 
thus yield two molecules of hydrogen and one molecule of 
oxygen. 

This is represented by the equation : 

2 H 2 = 2 H 2 + 2 

The reasons for regarding the oxygen (and hydrogen) mole- 
cules as consisting of two atoms need not be considered here. 
Conversely, when hydrogen burns in oxygen, the atomic 
theory regards the atoms of hydrogen and oxygen as uniting, 
two of the former with one of the latter, into molecules of 

water : 

2 H 2 + 2 = 2 H 2 

Before the reaction the atoms of hydrogen are united with 
each other in pairs, forming hydrogen molecules ; and the 
atoms of oxygen are united in pairs, forming oxygen mole- 
cules. After the reaction the atoms are combined in groups 
of three — two hydrogen and one oxygen — into molecules 
of water, thus, H — O — H. We commonly abbreviate the 
formula H— O— H into H 2 0. 



THE ATOMIC THEORY 3 1 

In such reactions as that of silver nitrate with sodium 
chloride (Expt. 6, p. 6) there is an exchange of partners 
among the atoms. Thus, the silver atoms separate from the 
nitrogen and oxygen atoms, with which they are originally 
united, and combine with the chlorine atoms of the sodium 
chloride, forming molecules of silver chloride ; and the 
sodium atoms, originally united with the chlorine atoms, 
transfer their allegiance from chlorine to nitrogen and oxygen. 

AgN0 3 + NaCl = AgCl + NaN0 3 

By measuring the proportions in which the elements com- 
bine with one another and reasoning from the results, chem- 
ists have arrived at definite conclusions regarding the rela- 
tive weights of the various kinds of atoms. Hydrogen, it is 
concluded, has the lightest atom. The oxygen atom is about 
sixteen (more accurately 15.87) times as heavy as the hydro- 
gen atom. The carbon atom is three-fourths as heavy as the 
oxygen atom or about twelve times as heavy as the hydro- 
gen atom. The heaviest atom known is that of uranium, 
which weighs about 237 times as much as the hydrogen 
atom. 

The relative weights of the atoms are given in the table on 
p. 33. A table of atomic weights might be made in which 
the weight of a hydrogen atom was taken as the unit. In 
such a table the atomic weight of oxygen would be 15.87, 
meaning that one atom of oxygen weighs 15.87 times as 
much as one atom of hydrogen, and the atomic weight of 
carbon would be 11.9, meaning that a carbon atom weighs 
1 1.9 times as much as a hydrogen atom. This was actually 
the basis upon which the first tables of atomic weights were 
made out. But the present international committee pre- 
fers to take the atomic weight of oxygen as exactly 16 and 
that of hydrogen as 1.008 (16 -f- 15.87 = 1.008). The ratio 
between any two atomic weights is the same on the one basis 
as on the other, and it is only the ratios which chemists profess 



32 ELEMENTARY HOUSEHOLD CHEMISTRY 

to know, the atoms themselves being immeasurably small, 
and therefore of unknown absolute weight. 

As already stated, the atomic theory in its modern form dates 
from the beginning of the nineteenth century. However, the 
view that matter is not infinitely divisible but is made up of minute 
indivisible particles (atoms) had been held by many philosophers 
of ancient times and by some of the great modern scientists who 
lived before Dalton's day, for instance, by Robert Boyle (1626- 
1691) and by Sir Isaac Newton (1642-1727). But the idea that 
each element has an atom of a definite weight, and that the smallest 
particles (molecules) of every compound are made up of atoms 
of the elements of that compound, originated with Dalton. 

The word atom (Greek, atomos, from a, not, and temno, cut) 
implies indivisibility. Until recently the atoms of the chemical 
elements were regarded as absolutely indivisible. The investi- 
gations arising out of the discovery of radioactivity have shown 
that some of the elements (especially some of those having very 
heavy atoms) are gradually undergoing a spontaneous trans- 
mutation into other elements of lower atomic weight. In under- 
going such transmutation these elements emit certain radiations, 
-some of which are believed to consist of particles much smaller 
than atoms. These particles are called electrons. Accordingly, 
it appears not improbable that the atomic theory will receive an 
extension, according to which the various kinds of atoms will 
be regarded as aggregations of various numbers of electrons. 

Up to the present no means have been found of controlling the 
transmutations of the radioactive elements. Accordingly, while 
it is no longer permissible to define an element as a substance 
which cannot be decomposed, it is still permissible for us to apply 
the term element to those substances which we cannot decompose, 
and the term atom to the theoretical particle which remains 
intact in all chemical changes that are not accompanied by radio- 
activity. 



THE ATOMIC THEORY 



33 



INTERNATIONAL ATOMIC WEIGHTS, 1913 



Element 


Symbol 


Atomic 
Weight 


Element 


Symbol 


Atomic 
Weight 


Aluminium . . 


. Al 


27.I 


Neodymium 


. Nd 


144-3 


Antimony . . 


. Sb 


I20.2 


Neon . . . 


. Ne 


20.2 


Argon . . . 


. A 


39-88 


Nickel . . . 


. Ni 


58.68 


Arsenic . . . 


. As 


74.96 


Niton (radium e 


ma- 




Barium . . 


. Ba 


137-37 


nation) . . . 


. Nt 


222.4 


Bismuth . . . 


. Bi 


208.0 


Nitrogen . . . 


. N 


14.OI 


Boron . . . 


. B 


11.0 


Osmium . . . 


. Os 


190.9 


Bromine . 


. Br 


79.92 


Oxygen . . 


. 


16.OO 


Cadmium . . 


. Cd 


112.40 


Palladium . . 


. Pd 


106.07 


Caesium . . . 


. Cs 


132.81 


Phosphorus . . 


. P 


31.04 


Calcium . . . 


. Ca 


40.07 


Platinum 


. Pt 


195.2 


Carbon . . . 


. C 


12.00 


Potassium . 


. K 


39.IO 


Cerium . 


. Ce 


140.25 


Praseodymium 


. Pr 


140.6 


Chlorine . . . 


. CI 


35-46 


Radium . . . 


. Ra 


226.4 


Chromium . 


. Cr 


52.0 


Rhodium 


. Rh 


102.9 


Cobalt . . 


. Co 


58.97 


Rubidium 


. Rb 


85.45 


Columbium . . 


. Cb 


93-5 


Ruthenium . 


. Ru 


IOI.7 


Copper . . 


. Cu 


63-57 


Samarium . 


. Sa 


150.4 


Dysprosium 


• Dy 


162.5 


Scandium 


. Sc 


44.I 


Erbium . . 


. Er 


167.7 


Selenium 


. Se 


79.2 


Europium . 


. Eu 


152.0 


Silicon . . 


. Si 


28.3 


Fluorine . . 


. F 


19.0 


Silver . . . 


• Ag 


107.88 


Gadolinium . . 


. Gd 


157.3 


Sodium . . 


. Na 


23.00 


Gallium . . . 


. Ga 


69.9 


Strontium . 


. Sr 


87.63 


Germanium 


. Ge 


72.5 


Sulphur . . 


. S 


32.07 


Glucinum 


. Gl 


9.1 


Tantalum 


. Ta 


181.5 


Gold . . . . 


. Au 


197.2 


Tellurium 


. Te 


127.5 


Helium . . 


. He 


3-99 


Terbium . . 


. Tb 


159.2 


Holmium . . 


. Ho 


163.5 


Thallium . . 


. Ti 


204.O 


Hydrogen 


. . H 


1.008 


Thorium . . 


. Th 


232.4 


Indium . . 


. . In 


114.8 


Thulium . . 


. . Tm 


168.5 


Iodine . . 


. . I 


126.92 


Tin . . . 


. . Sn 


119.0 


Iridium . . 


. . Ir 


i93-i 


Titanium 


. Ti 


48.I 


Iron . . . 


. . Fe 


55-84 


Tungsten 


. . W 


184.O 


Krypton . . 


. . Kr 


82.92 


Uranium 


. . U 


238.5 


Lanthanum . 


. . La 


139.0 


Vanadium . 


. . V 


5I.O 


Lead . . . 


. . Pb 


207.10 


Xenon . . 


. . Xe 


130.2 


Lithium . 


. . Li 


6.94 


Ytterbium (K 


eo- 




Lutecium 


. . Lu 


174.0 


ytterbium) 


. . Yb 


172.O 


Magnesium . 


■ • Mg 


24.32 


Yttrium . . 


. . Yt 


89.O 


Manganese . 


. . Mn 


54-93 


Zinc . . . 


. . Zn 


65.37 


Mercury . . 


. • Hg 


200.6 


Zirconium . 


. . Zr 


90.6 


Molybdenum 


. . Mo 


96.0 









CHAPTER VII 

THE LAW OF DEFINITE PROPORTIONS 

It Dalton's atomic theory be correct, every compound 
must contain its elements in certain definite proportions by 
weight. Thus a water molecule, made up of two atoms of 
hydrogen, weighing 2 (or more precisely 2.016), and one 
atom of oxygen weighing 16, has evidently 8 times as much 
of oxygen by weight as of hydrogen. And since a cupful 
(or a barrelful) of water is made up of individual molecules, 
every one of which contains 8 times as much oxygen as 
hydrogen, the cupful (or barrelful) of water if decomposed 
would yield 8 times the weight of oxygen as of hydrogen. 
Experiment shows that this is true no matter what the 
quantity of water used. The same principle applies to 
every compound. 

A chemical compound always contains the same elements in 
the same proportions by weight. This is known as the Law of 
Definite Proportions. 

This principle of Definite Proportions is not confined to 
reactions of combination. It governs chemical reactions 
of all kinds. 

The molecule of calcium carbonate, CaC03, being made 
up of one atom of calcium, weighing 40, one atom of carbon, 
weighing 12, and three atoms of oxygen, each weighing 16, 
has a total weight of 40 + 12 + 48 = 100. Similarly, the 
molecular weight of calcium oxide, CaO, is 56 (40 + 16) and 
that of carbon dioxide, C0 2 , is 44 (12 + twice 16). Accord- 
ing, then, to the equation 

CaC0 3 = CaO + C0 2 
100 parts of calcium carbonate decompose into 56 parts of 
calcium oxide and 44 parts of carbon dioxide. And this is 

34 



THE LAW OF DEFINITE PROPORTIONS 35 

true, whatever the units in which we express the weight. 
Thus 100 grains of calcium carbonate give 56 grains of cal- 
cium oxide and 44 grains of carbon dioxide ; 100 ounces of 
calcium carbonate give 56 ounces of calcium oxide and 44 
ounces of carbon dioxide ; and so on for pounds, tons, grams, 
kilograms, and all other units of weight. 

So also 170 parts of silver nitrate by weight react with 
58.5 parts of salt (sodium chloride), no more and no less : 





AgN0 3 


+ 


NaCl = 


AgCl + NaN0 3 




170 




58.5 


143-5 85 


Ag = 




108 


Na = 35.5 


Ag = 108 Na = 23 


N = 




14 


CI = 23.0 


Cl= 35.5 N= 14 


3 = 


16X3 = 


=_48 




3 0= 48 






170 


58.5 


143-5 85 



Every pound of silver nitrate takes 58.5 -s- 170 = 0.344 
pound of salt, and every Ion of silver nitrate 0.344 ton of salt. 
If more salt is used, the excess will be left unchanged. If, for 
instance, one pound of silver nitrate and one pound of salt are 
brought together in solution, 0.344 pound of the salt will be 
used up in precipitating the silver nitrate and the remaining 
0.656 pound of salt will be left in the water unchanged. 

This principle is of some importance in the household 
applications of chemistry. Baking powders, for instance, 
should be so made as to contain exactly the right quantity 
of soda to react with all the cream of tartar. If too much 
of either constituent is used, the excess will remain in the 
cake or biscuit, making it sour or bitter as the case may be. 

EXERCISES 

1. The reaction between baking soda and cream of tartar is 
represented by the equation : 

NaHC0 3 + KHC 4 H 4 6 = KNaC 4 H 4 6 + C0 2 + H 2 

Sodium bicar- Potassium Potassium Carbon 

bonate or bitartrate or sodium tar- dioxide 

baking soda cream of trate or 

tartar Rochelle salt 



36 ELEMENTARY HOUSEHOLD CHEMISTRY 

Using the atomic weights of the table on the inside of the back 
cover of the book, calculate how many pounds of pure cream of 
tartar are required for every pound of baking soda. 

2. How many ounces of carbon dioxide are obtainable from a 
pound (16 ounces) of baking soda by the reaction with cream of 
tartar ? 

3. 100 pounds of cream of tartar 90 per cent pure are to be 
made up into baking powder. How many pounds of pure baking 
soda should be used? 

4. When baking soda is heated, washing soda (Na 2 C03) is 
formed according to the following equation : 

2 NaHC0 3 = Na 2 C0 3 + H 2 + C0 2 

This equation signifies that two molecules of sodium bicar- 
bonate are converted into one each of sodium carbonate, water, 
and carbon dioxide. 

How many pounds of washing soda would 100 pounds of 
baking soda make ? 

5. 100 grams each of baking soda and pure cream of tartar are 
mixed and used as a baking powder in making a batch of biscuits. 
How much baking soda will be left over when the cream of tartar 
has all been acted upon? 

6. Assuming that the baking soda left over in Example 5 is all 
converted into washing soda in the baking, how many grams of 
washing soda will the batch of biscuits contain ? 

Experiment 23. 

Materials : 

Potassium bitartrate. 

Sodium bicarbonate. 

Litmus solution. 

25 cc. graduated cylinders. 
Dissolve 1.88 grams potassium bitartrate in 50 cc. of hot water 
in a beaker. Keep the liquid hot, but not boiling, and stir with 
a glass rod until all the solid is dissolved. Dissolve 0.84 gram 
sodium bicarbonate in 20 cc. of cold water. Divide each solution 
into two exactly equal portions. To one portion of each add 
enough litmus solution to color it distinctly. Observe the color 
the litmus takes in the two liquids. Put the colored bicarbonate 
solution into a beaker or dish and gradually pour the colored 
bitartrate solution (still hot) into it. What do you observe? 
Hold a film of limewater (calcium hydroxide) in the escaping gas. 



THE LAW OF DEFINITE PROPORTIONS 37 

What is this gas? If the color of the bicarbonate solution is not 
changed, add some of the second portion of bitartrate solution 
little by little, until the color does change. Then add the un- 
colored portion of bicarbonate solution, and finally the remainder 
of the bitartrate solution. If necessary, dissolve a little more 
bitartrate and add it. If the materials are perfectly pure (which 
they often are not) and the weighings exact, the color changes 
will occur when the half portion of the two solutions are mixed 
and again when the whole of the bitartrate solution has been added. 



CHAPTER VIII 

COMPOUNDS OF THE SAME ELEMENTS IN DIF- 
FERENT PROPORTIONS 

If different numbers of atoms of two elements combine, 
the molecules formed are different. Thus, there is a liquid 
substance, similar in appearance to water, which yields by 
decomposition 16 times as much oxygen by weight as hydro- 
gen, i.e. equal volumes of the two gases. This substance is 
known as hydrogen peroxide. A mixture of 3 parts of it 
with 97 parts of water (a 3 per cent solution) is a common 
article of commerce, being used as a bleaching agent and as 
an antiseptic. Now, the molecule of hydrogen peroxide 
must contain 16 times as much oxygen as hydrogen; that is 
to say, one atom of oxygen to every atom of hydrogen. It 
is believed to contain two atoms of each element and is there- 
fore given the formula H 2 2 . 

Similarly, we have two compounds of oxygen and carbon, 
both gases, (1) carbon monoxide, CO, and (2) carbon dioxide, 
CO2; two oxides of copper, viz. (1) cuprous oxide, CU2O, 
a red solid, and (2) cupric oxide, CuO,a black solid ; and two 
chlorides of iron, viz. (1) ferrous chloride, FeCl 2 , a greenish 
solid, and (2) ferric chloride, FeCl 3 , a reddish solid ; and 
there are many other instances of the existence of more than 
one compound of the same elements. Indeed, there are 
several hundred compounds of the elements carbon and hy- 
drogen (hydrocarbons) and thousands of compounds of the 
three elements carbon, hydrogen, and oxygen. 

38 



COMPOUNDS OF THE SAME ELEMENTS 39 



Nomenclature of Such Compounds 

Where the number of different compounds of the same 
elements is limited to two, the two are often distinguished 
by using the suffixes -ous and -ic on the adjective part 
of the name. The suffix -ous — signifying " full of " l — is 
applied to the compound containing the larger proportion of 
the element to whose name the suffix is attached. Thus : — 

Cuprous oxide, Cu 2 ; Cupric oxide, CuO. 

Ferrous chloride, FeCl 2 ; Ferric chloride, FeCl 3 . 

Sulphurous acid, H2SO3 ; Sulphuric acid, H 2 S0 4 . 

Mercurous chloride, HgCl ; Mercuric chloride, HgCl2. 

Ferrous sulphate, FeS0 4 ; Ferric sulphate, Fe 2 (S0 4 )3. 

Ferrous chloride has one atom of iron to every two atoms of 
chlorine, while ferric chloride has only one atom to every three; 
sulphurous acid has one of sulphur to every three of oxygen, while 
sulphuric acid has only one to every four, etc. 

EXERCISES 

Name the following compounds on the above principle : 

(1) CuCl and CuCl 2 . (2) AuCl and AuCl 3 . 

(3) HgN0 3 and Hg(N0 3 ) 2 . (4) SnCl 2 and SnCl 4 . 

(5) HC10 2 and HC10 3 (acids). (6) H 3 P0 3 and H 3 P0 4 (acids). 

Another means of distinguishing compounds of the same elements 
in different proportions is to modify the substantive part of the 
name with a prefix indicating the number of atoms of the element, 
whose name is thus modified, contained in the molecule of the 
compound. The prefixes used are derived from the Greek 
numerals : 

Mono- or mon-, one; di-, two; tri-, three; tetra- or tetr-, four; 
penta- or pent-, five ; hexa- or hex-, six ; hepta- or hept-, seven ; 
octo- or oct-, eight ; etc. 

Carbon monoxide, CO ; Carbon dioxide, C0 2 . 

Nitrogen trioxide, N 2 3 ; Nitrogen pentoxide, N 2 5 . 

The prefix per-, signifying " thorough," is sometimes used to 
denote that the compound named has more of a certain element 

1 Compare such words as dangerous, beauteous, mysterious, and tyrannous. 



40 ELEMENTARY HOUSEHOLD CHEMISTRY 

(usually oxygen) than some other compound. Thus : hydrogen 
peroxide, H 2 2 , has more oxygen than water, H 2 ; and barium 
peroxide, Ba0 2 , more oxygen than barium oxide, BaO. Also 
perchloric acid, HCIO4, has more oxygen than chloric acid, 
HCIO3, and perboric acid, HBO3, a larger proportion of oxygen 
(e.g. to one atom of hydrogen) than boric acid, H3BO3. 

EXERCISES 

Name the following: 

(1) PCI3, (2) PCI5, (3) P2O3, (4) P2O5, (5) S0 2 , (6) S0 3 , (7) PbO, 
(8) Pb0 2 . 



CHAPTER IX 

COMBUSTION 

One of the most familiar, as well as one of the most use- 
ful, of chemical phenomena is combustion or burning. Fire 
has been known to mankind from time immemorial, and 
advance in its control and utilization has kept pace with 
the progress of civilization. Even to-day, when electrical 
energy is so much made use of, practically our only source 
of artificial heat is combustion. Our rural homes, for the 
most part, depend upon combustion, not merely for heat 
but also for light, and even the electricity which lights our 
towns and cities comes largely from power generated by 
the burning of coal. 

Combustion can take place either with or without the 
phenomenon of flame. Flame appears in the burning of 
paper, wood, coal, candles, oils, alcohol, and gas. Charcoal 
and coke, however, burn without flame. As charcoal is 
made by heating wood, and coke by heating coal, we have 
nameless combustion in the later stages of wood and coal 
fires. 

Experiment 24. 

Materials : 
Test tube. 

Pieces of hard wood. 

Cork and cork borer, or one-holed rubber stopper. 
Glass tube drawn to a tip at one end. 
Provide a test tube with a tightly fitting, single-hole cork or 
rubber stopper, through which passes a short piece of glass tubing 
drawn to a tip at the upper end. Place a piece of dry, hard wood 
in the test tube, and apply heat. Apply a match to the smoke 
which issues from the glass tip. The visible part of the smoke 

41 



42 



ELEMENTARY HOUSEHOLD CHEMISTRY 



consists of small particles of solid matter and minute drops of 

liquid. But these solid particles 
and liquid droplets are suspended 
in invisible gases, which are them- 
selves combustible. When the 
gas ceases to burn and will not 
relight, open the test tube and 
examine the residue left from the 
wood. What is it? Heat one 
end of it in the Bunsen flame for 
a minute or two. On withdraw- 
ing it from the flame note whether 
it is burning, and if so, whether 
with or without flame. 

In the light of this experiment, 
how do you account for the fact 
that a wood fire shows flame in 
its early stages, but later no flame 
but only glowing coals ? 



Experiment 25. 

Materials : 

Hard-glass test tube. 
Soft coal in small pieces. 
Repeat Experiment 24 in a 
hard-glass test tube, using soft 
coal instead of hard wood. The 




Fig. 23. — Apparatus for destructive 
distillation of wood or coal. 



residue left in the test tube in this instance is coke. 



Experiment 25 illustrates the process of manufacture 
of the illuminating gas known as " coal gas." Before the 
gas is delivered into the mains to be distributed it is purified 
by the removal of the solid and liquid particles which con- 
stitute the cloud. In the purification processes some of the 
gaseous products also are eliminated — for instance, sul- 
phur compounds, the burning of which would yield products 
injurious to health. 

Flame occurs only in the combustion of gases. Solid 
and liquid fuels which burn with flame do so because they are 
converted, wholly or partially, into gases by the heat pro- 




John Mayow. — 1 645-1 679. 

Mayow, an English physician, recognized that air contained a constitu- 
ent concerned in combustion, in respiration, and in the rusting of metals. 
He estimated that this active constituent made up about one fourth of the 
air and found that it was present in saltpeter. Mayow called the active 
substance " fire-air " and " nitre-air." We call it oxygen. 



x 



COMBUSTION 



43 



duced by the combustion. The reason that charcoal and 
coke burn without flame is that (except for the ash which 
they contain) these fuels consist wholly of the element 
carbon, which is not converted into gas by the heat of its 
own combustion. The solid carbon combining with the gas 
oxygen yields much heat — so much that it is heated to 
incandescence — but no flame. 

We have next to consider the part the gases of the air 
play in the process of combustion. 

Experiment 26. 

Materials : 

Supply of nitrogen from a generator or gasometer. 

Supply of oxygen from a generator or gasometer. 

Splint. 

Candle. 

Labels. 
Plunge a flaming splint into (1) a 
bottle of air, (2) a bottle of oxygen, 
(3) a bottle of nitrogen. Do the 
same with a lighted candle. 

Experiment 27.* 

Apparatus : 
A bell glass with open narrow 
neck. Rubber stopper to fit. 
A basin or stoppered sink, or 

pneumatic trough. 
A porcelain crucible. 
A wire stand for the crucible 
about \ the height of the bell. 
A straight, stiff, iron wire, longer 

than the height of the bell. 
A candle on a bent wire. 
Materials : 

Phosphorus under water. (Dangerous ! Handle only with 

tongs.) 

^ Support a crucible on a wire stand in a basin, glass trough, or 

sink containing water. Dry a small piece of phosphorus on filter 

paper and transfer to the crucible with tongs. Invert the open 




Fig. 24. — Apparatus for Ex- 
periment 27. Removing 
the oxygen from the air by 
burning phosphorus. 



44 



ELEMENTARY HOUSEHOLD CHEMISTRY 



l\ 



bell glass over the crucible. Heat the iron wire in a flame, touch 
it to the phosphorus, immediately withdraw the wire from the 
bell and insert the stopper. The water in the basin should be 
deep enough to prevent the escape of any air 
on account of the expansion due to the burn- 
ing. Allow to stand until the fumes have set- 
tled and the glass has cooled to the room 
temperature (10 or 15 minutes), pouring suffi- 
cient water into the basin from time to time to 
keep the inner and outer levels equal. Remove 
the stopper and lower into the bell (a) a lighted 
candle, (b) a flaming splint. 

Compare the results with those obtained with 
air and with nitrogen in Experiment 26. 

Experiment 28. 

Fill a wide-mouthed bottle with water and 
pour out the water into a graduated cylinder. 
Note the quantity of water (number of cubic 
centimeters) and pour it back into the bottle in 
five equal portions, marking the level of each 
Cover the full bottle tightly with a glass plate, 
and invert it into a trough of water. Deliver oxygen into the 
bottle until one-fifth of the water is displaced. Displace the re- 
maining four-fifths similarly with nitrogen. Again cover the 
mouth of the bottle with the glass plate, and turn the bottle over 
several times to mix the gases. Test this mixture with a lighted 
splint or a lighted candle, comparing the result with those ob- 
tained in Experiment 26. 

Experiment 29. 

Apparatus : 
Pan. 
Candle. 

Wide-mouthed bottle. 
Attach a candle to the bottom of a pan, and cover the bottom 
of the pan with water. Light the candle, and invert over it the 
wide-mouthed bottle divided into fifths (Expt. 28). Is the flame 
extinguished immediately? After a time? Allow to stand until 
cool. How much has the air decreased in volume? 

Invert pan and bottle over a sink, allowing the water in the pan 
to fall out. Remove the pan and immediately test the gas in 



Fig. 25. — Candle 
on bent wire. 

-fifth with a label. 




Joseph Priestley. — 1733-1804. 

An English Unitarian minister, accredited with the discovery of oxygen 
(1774), because he was the first to describe the pure substance. Persecuted in 
England for his religious and political views, Priestley emigrated to the United 
States, settling in Northumberland, Pennsylvania, where he spent the last ten 
years of his life. 



COMBUSTION 



45 



the bottle with a flaming splint or candle. Which of the two air 

gases was left in the bottle ? 




Fig. 26. — Experiment 2Q. 
Burning a candle in a 
bottle of air. 




Fig. 27. — Experiment 2Q. 
Inverting the bottle to ex- 
amine the residual gas. 



When a splint or candle or any fuel substance is burned 
in air, the oxygen of the air disappears and the nitrogen 
remains. We must next inquire what becomes of the oxygen. 

Experiment 30. 

Materials : 
Candle. 
Wide-mouthed bottle. 

Over a lighted candle invert a dry, cold, wide-mouthed bottle. 
Note the mist which gathers on the inside of the bottle. This 
consists of droplets of water. Cover the bottle, turn it right side 
up, pour in a little limewater, and shake. What gas must have 
been formed in the combustion of the candle ? 

What products are formed in the combustion of illuminating 
gas? (See Expt. 12.) 

When a candle burns, it obviously loses weight. But 
we have just seen that the gases, steam and carbon dioxide, 
are products of the combustion. In open-air combustion 
these gases are constantly being swept away from the burn- 
ing substance by the air currents. It will be interesting to 
examine whether, when these gases are retained and weighed 
along with the diminished candle, there has been any loss 
of weight. The following experiment determines this point. 



46 



ELEMENTARY HOUSEHOLD CHEMISTRY 



Experiment 31.* 

Apparatus : 

Balance. 

Sodium hydroxide in sticks. 

Two lamp chimneys or open glass cylinders. 

Candle. 

Wire gauze. 
Close the lower ends of the lamp chimneys with wire gauze, 
and fill them with approximately equal quantities of sodium 
hydroxide, a substance which will take up both the water and the 
carbon dioxide. Attach the candle to a card or flat cork, and fix 
it beneath one of the cylinders of caustic soda. Suspend the 




Fig. 28.' — Experiment 31. Comparing the weight of an unburned candle with 
that of a burning candle and the products of its combustion. 

chimneys from the hooks of the balance and counterpoise the 
balance, e.g. with sand. Light the candle, and note whether the 
system becomes lighter or heavier when the products of the 
combustion are not allowed to escape. Account for the fact that 
the weight does not remain unchanged. 

Burning in an abundant supply of oxygen, the elements 
carbon and hydrogen, respectively, combine with oxygen, 
forming carbon dioxide and water. These same products 




Antoine-Laurent Lavoisier. — 1743-1794 

Lavoisier originated the modern theory of combustion and respira- 
tion and discredited the idea, prevalent in his time, that in combustion 
something called "phlogiston" escaped from the burning substance. 
Being connected with the French government at the time of the Revo- 
lution, Lavoisier was guillotined. 



X 



COMBUSTION 47 

are formed in the combustion of all compounds of carbon 
and hydrogen, and of all compounds of carbon, hydrogen, 
and oxygen. No other products than carbon dioxide and 
water are formed unless (i) other elements are present, or 
(2) the conditions are such that the combustion is not com- 
plete. Carbon dioxide and water vapor are not poisonous. 
They are present in small quantities, even in the purest of 
outdoor air. On the other hand, the products of combustion 
of some of the other elements, e.g. sulphur and arsenic, are 
injurious to the health, and so also are some of the products 
of incomplete combustion of carbon and of compounds of 
carbon and hydrogen, or of carbon, hydrogen, and oxygen. 
The most dangerous of these poisons is the colorless gas, 
carbon monoxide, CO, which has the property of combining 
with that constituent of the blood (hemoglobin) whose 
function it is to take up oxygen in the lungs and convey it 
to other parts of the body. Hemoglobin which has com- 
bined with carbon monoxide cannot combine with oxygen. 
Hence, carbon monoxide poisoning completely deranges the 
respiration and quickly produces fatal results. It is impor- 
tant that the student of household science should have some 
knowledge of this poisonous gas. 

Experiment 32.* 

Apparatus : 

Carbon dioxide generator. 

Iron tube. 

Furnace (see Fig. 29). 

3 Woulff bottles. 

Pneumatic trough. 

Glass cylinder. 

Connections. 
Materials : 

Charcoal in lumps. 

Potassium hydroxide, 30 per cent solution. 
Pass a slow current of carbon dioxide into a train of apparatus 
comprising (1) a Woulff bottle containing concentrated sulphuric 



48 



ELEMENTARY HOUSEHOLD CHEMISTRY 



acid, (2) an iron tube packed with charcoal and heated to redness 

in a furnace, (3) 2 Woulff 
bottles containing 30 per cent 
potassium hydroxide, (4) a 
delivery tube leading to a 
cylinder of water inverted in 
a pneumatic trough. (See 
Figure 29.) The carbon di- 
oxide gas from the generator 
is dried by bubbling through 
the sulphuric acid. That 
part of the gas which is not 
acted upon by the red-hot 
carbon in the iron tube is 
absorbed by the potassium 
hydroxide solution in the two 
Woulff bottles. The carbon 
monoxide gas is formed by 
the action of the carbon on 
the carbon dioxide, thus : 

C0 2 + C = 2 CO 

and this gas passes over into 
the pneumatic trough, where 
it is collected by displace- 
ment of water. 

Reject the first two or 
three cylinders of the col- 
lected gas, this being in part 
the air originally present in 
the apparatus. Test the gas 
subsequently collected by 
applying a burning splint. 
Note the color of the flame. 
When the gas is all burnt, 
pour a little calcium hydrox- 
ide solution (limewater) into 
the cylinder, and shake. 
What gas is formed in the 
combustion of carbon mon- 
oxide ? 




COMBUSTION 49 

Carbon monoxide is formed in coal stoves and furnaces, 
and burns with a blue flame at the top or back of the fire, 
where it meets with more air. Some of the carbon dioxide 
formed at the bottom of the fire is " reduced " (the word 
reduced is used in chemistry in the sense of " deprived 
of oxygen ") to carbon monoxide, by the red hot carbon 
of the fire, just as carbon dioxide was reduced to carbon 
monoxide in our experiment. If the draft is poor, some 
of this poisonous gas may escape from the stove and con- 
taminate the air of the house. It requires only i to J per 
cent of carbon monoxide in -the air of a room to have a 
fatal effect upon the human occupants if they remain exposed 
to it for any considerable length of time, and even yo per 
cent is decidedly injurious. Inhaled in small quantities, 
carbon monoxide causes dullness, sleepiness, and headache. 
Being odorless and stupefying, it is a very insidious poison. 
Fortunately, odorous gases usually escape with it, and 
these may suggest its possible presence to one on the lookout 
for it. Persons poisoned with the gas should be immedi- 
ately taken into the open air and made to breathe deeply. 
In the event of unconsciousness or stupefaction artificial 
respiration should be established, as in the treatment for 
drowning. This consists in alternately extending the arms 
above the head and pressing them firmly against the chest. 

An easier but less instructive way of preparing carbon 
monoxide depends upon the so-called dehydrating action 
of concentrated sulphuric acid. In Experiment 32 con- 
centrated sulphuric acid was used to dry the carbon dioxide, 
i.e. to take up the water vapor mixed with the gas. Now, 
concentrated sulphuric acid not only takes up free water 
molecules, as in the above instance, but actually breaks 
up many molecules by withdrawing the elements of water 
from them. Formic acid, H 2 C0 2 , is one of the substances 
which is decomposed in this way by sulphuric acid. If we 
examine the formula of formic acid, we see that the removal 

E 



5° 



ELEMENTARY HOUSEHOLD CHEMISTRY 



of a molecule of water from a molecule of formic acid leaves 
a molecule of carbon monoxide. 

H 2 C0 2 = H 2 + CO 

Carbon monoxide may, therefore, be prepared as follows: 




Fig. 30. — Experiment 33. A pparatus for the generation of carbon 
monoxide from formic acid. 

Experiment 33.* 

Materials : 

Formic acid solution (or a strong solution of sodium formate). 
Crude sulphuric acid. 
Apparatus : 

Flask provided with a dropping funnel and a delivery tube. 
Pneumatic trough. 
Cylinders or bottles. 
Connections. 
Allow the formic acid or sodium formate solution to drop slowly 
upon the concentrated sulphuric acid, and collect the gas by dis- 
placement of water. 



CHAPTER X 

THE RELATION OF COMBUSTION TO HEAT 

Heat is not a substance in the sense in which the word 
substance is used in chemistry. If we weigh a body cold 
(say a platinum crucible), then heat it and weigh it again, 
we find that in spite of the addition of heat there is no increase 
of weight. Had we added any substance to the platinum, 
the weight would have increased. There is no molecule 
of heat. On the contrary, heat is regarded as consisting in 
molecular motion, the molecules of hot bodies vibrating 
back and forth more rapidly than those of cold bodies. (See 
Chapter VI.) That mechanical work or energy can be con- 
verted into heat is illustrated by the primitive methods of 
obtaining fire practiced by savage races, such as the rubbing 
together of two sticks of wood, or the twirling of one stick 
upon a hollowed part of a second stick. The same prin- 
ciple was demonstrated on a larger scale in 1798 by Count 
Rumford, who, by an experiment performed publicly before 
the Elector of Bavaria, showed that in boring a cannon with 
a blunt borer it is possible to heat over 25 pounds of water to 
the boiling point in about two hours and a half. 

That, conversely, work can be obtained from heat is 
illustrated by the steam engine, which is a machine devised 
for that very purpose. 

Heat is therefore a form of energy, and the study of heat 
belongs to the domain of physics. On account of its relation 
to combustion, however, it is desirable that we have clear 
conceptions of the meanings of some words relating to heat. 

Temperature is a familiar term. A hot body is said to 
have a high, and a cold one, a low temperature. Instruments 

51 



52 ELEMENTARY HOUSEHOLD CHEMISTRY 

used to measure temperature are called thermometers. Two 
styles of thermometers are in common use in America — 
the Fahrenheit and the Centigrade, or Celsius. Placed in 
melting ice or in freezing water the Fahrenheit thermometer 
registers 32 degrees; the Centigrade thermometer, zero. 
Placed Jn the vapor of boiling water the Fahrenheit ther- 
mometer registers 212 degrees; the Centigrade, 100 degrees. 
Thus the interval between the freezing and boiling points of 
water is divided on the Fahrenheit thermometer into 180 
degrees, and on the Centigrade thermometer into 100 degrees. 
In other words, 100 Centigrade degrees =180 Fahrenheit 
degrees, or 1 Centigrade degree = 1.8 Fahrenheit degrees. 

The quantity of heat in a body depends not only on its 
temperature, but also on its mass and on the substance of 
which it is composed. Thus, while a cupful of boiling water 
and a barrelful of boiling water have exactly the same tem- 
perature they contain very different quantities of heat. 
Instruments used to measure quantity of heat are known as 
calorimeters. (See p. 55.) 

Various units of quantity of heat have been proposed. 
We shall define two — the Calorie (" large calorie " or 
" kilogram calorie " l ) and the British Thermal Unit (B. T. U.). 

A Calorie is the quantity of heat that will raise the tem- 
perature of one kilogram of water one degree Centigrade. 

A British Thermal Unit is the quantity of heat that will raise 
the temperature of one pound of water one degree Fahrenheit. 

A Calorie is approximately equal to 4 British Thermal 
Units. 2 

1 A "small" or "gram" calorie is the quantity of heat that, will raise the 
temperature of one gram of water one degree Centigrade. One Calorie (spelled 
with a capital) is therefore equal to iooo calories (spelled with a small c). It 
should be noted, however, that in books in which there is no reference to small 
calories the large calorie may be found spelled without the capital. 

2 1 Kilogram = 2.2 lb. 

1 Centigrade degree = 1.8 Fahrenheit degrees. 
.'. 1 Calorie = 2.2 X 1.8 = 3.96 B.T. U. 




Sir Benjamin Thompson, Count Rumford. — 1753-1814. 

Who demonstrated the production of heat by friction. Born at Woburn, 
Massachusetts, Thompson removed to England early in the War of Independ- 
ence and later returned in command of British troops, which did not see ac- 
tive service. In 1783 he entered the service of the Elector of Bavaria, be- 
coming a minister of state. For his services to Bavaria he was created a 
Count of the Holy Roman Empire, his title of Rumford being derived from 
the New Hampshire town (now Concord), where he had taught school. Re- 
turning to England in 1795, he projected the Royal Institution and selected 
Sir Humphry Davy as its first scientific lecturer. The last ten years of his 
life were spent in France, where he married the widow of the great French 
chemist, Lavoisier. Amongst his numerous interests Rumford devoted much 
attention to problems of cooking, clothing, and fuel economy. 



\ 



THE RELATION OF COMBUSTION TO HEAT 53 

Ignition Temperature 

Experiment 34. 

Materials : 

Disks of sheet iron or tinned iron 4 inches in diameter. 
Coke, charcoal, yellow phosphorus (under water), red phos- 
phorus, sulphur, pine, and soft coal. 
Forceps to handle the yellow phosphorus. 
Filter paper to dry the yellow phosphorus. 
At equal distances from the center of a circular piece of metal, 
e.g. the cover of a tin, supported on a tripod or an iron ring, place 
small portions of coke, charcoal, red phosphorus, yellow phos- 
phorus, sulphur, pine, and soft coal. Place a Bunsen flame exactly 
under the center of the metal, and note the order in which the 
materials take fire. 

It is a familiar fact that most substances must be heated 
before they will burn, and that some substances must be 
made much hotter than others. Everybody knows, for 
instance, that anthracite coal (hard coal) cannot be ignited 
as easily as pine wood. Every substance may be said to have 
its ignition temperature. Thus, while some kinds of dry 
peat will ignite at 200 C, and charcoal in pure oxygen 
ignites at 345 C, graphite will not take fire below 690 C. 
in pure oxygen, nor diamond below 8oo° C. (Charcoal, 
graphite, and diamond are three modifications of the element 
carbon.) A few substances will ignite at ordinary atmos- 
pheric temperatures, but such are rare and unimportant. 

Matches are tipped with substances of ignition tempera- 
tures sufficiently low to be attained by friction. Yellow 
phosphorus, covered with a protective coating, has been much 
used for this purpose, but is now prohibited in most civilized 
countries, on account of its injurious effects upon the health 
of the factory operatives. Red phosphorus is free from this 
objection, and so is the compound phosphorus pentasul- 
phide, P2S5. Matches can also be made without any phos- 
phorus. Indeed, the earliest friction matches (known as 



54 



ELEMENTARY HOUSEHOLD CHEMISTRY 



lucifer matches or " Congreves " l ) were tipped with a 
phosphorus-free mixture, consisting of antimony sulphide, 
potassium chlorate, starch, and gum. 

Safety matches are tipped with a mixture that is difficult 
to ignite by simple friction, but which ignites when rubbed 
upon a second mixture (containing red phosphorus) which 
is applied to the surface of the match box. 

Heat of Combustion 

The heat of combustion of a substance is the quantity 
of heat produced when a given quantity (one 
pound or one gram) of the substance is com- 
pletely oxidized. The heat of combustion of any 
substance is always the same whether the sub- 
stance burns rapidly, e.g. in compressed pure 
oxygen, or more slowly, as in air; or even oxi- 
dizes slowly without the phenomena of combus- 
tion. The temperature attained during the oxi- 
dation is, however, greater the more rapidly the 
substance burns. 

Experiment 35.* 

Materials". 

Bottle of oxygen. 

Small pieces of yellow phosphorus in a dish of 

water. 
Deflagrating spoon. 
Forceps. 
Porcelain dish. 
With the forceps remove one piece of phosphorus 
from the water, place it on filter paper for a 
moment to dry, then leave it in the dry porcelain 
dish exposed to the air. Dry a second piece, transfer 
it to the deflagrating spoon, and ignite it by warming. 
Dry a third piece, ignite it in the deflagrating 
spoon, and immediately plunge it into the oxygen. 

1 So named by the inventor, John Walker, in 1827, in honor of Sir William 
Congreve. 



Fig. 31. — A 
deflagrating 
spoon. 



THE RELATION OF COMBUSTION TO HEAT 



55 



In the experiment just performed the higher temperature 
attained in the more rapid 
combustion is made ap- 
parent by the greater bril- 
liance and smaller volume 
of the flame. Careful ex- 
periment with a calorimeter 
shows that the quantity of 
heat set free in the oxida- 
tion of a given amount of 
phosphorus is identical in 
the three instances. But 
the same quantity of heat, 
set free in a smaller space 
and at a more rapid rate, 
produces a higher tempera- 
ture. 

To measure heats of com- 
bustion accurately the com- 
bustion is caused to take 
place as rapidly as possible, 
and the heat produced is 
used to heat water. To 
this end a weighed quantity 
of the substance, whose 
heat of combustion is to 
be determined, is burned 
in compressed oxygen in a 
steel bomb. (See Fig. 32.) 
The bomb is immersed in 
a vessel of water, into which 
a thermometer dips. The 
heat produced in the com- 
bustion heats the water surrounding the bomb. Knowing 
the weight of this water, and how much its temperature is 




Fig. 32. — A bomb calorimeter. The 
substance in the bomb is ignited by 
an electrical device. The platinum 
wires, H and I, the former of which 
is insulated from the steel of the bomb, 
are connected inside the bomb by a 
little coil of iron wire just above the 
capsule, 0, which contains the sub- 
stance to be burned. An electric 
current, passed through these wires 
for a few seconds, heats the iron wire 
to redness, when it burns, and, falling 
on the substance in the capsule, sets 
it on fire. 5 in the figure is a stirrer, 
which is kept in constant motion to 
keep the water well mixed. 



56 ELEMENTARY HOUSEHOLD CHEMISTRY 

raised, we can easily calculate the number of calories or 
British Thermal Units of heat that have gone into it. If, 
for instance, 2 pounds of water have been heated 2 Fahren- 
heit degrees, we know that 2X2 = 4 B. T. U. must have 
gone into the water. 

When 12 pounds of carbon (one atomic weight in pounds) 
are burnexl to carbon dioxide, 174,500 B. T. U. are set free. 
When the quantity of carbon monoxide containing 12 
pounds of carbon (viz. 28 pounds) is burned, 122,400 B. T. U. 
are set free. From this we infer that when 12 pounds of 
carbon are burned to carbon monoxide, only 52,100 B. T. U. 
are liberated. In other words, any carbon monoxide allowed to 
escape up the chimney unburned involves a loss of more than 
two-thirds of the heat the carbon contained in it was capable 
of yielding. It is, therefore, bad economy to have the upper 
part of a coal stove or furnace so tightly closed that air 
cannot enter to burn the carbon monoxide. Moreover, if the 
carbon monoxide is not burned, there is danger that some 
of this extremely poisonous gas may escape into the room. 
A blue flame on the top of a coal fire is evidence that the 
carbon monoxide is burning. 

Propagation of Combustion 

Fire once started has a tendency to spread. This is 
because, once a portion of the combustible substance is in 
active combustion, the heat set free raises neighboring- 
portions to the kindling point. In solid and liquid fuels 
burning with a flame, a part of the heat produced by the com- 
bustion is used in converting the solid or liquid into the 
gaseous condition. In gases all the heat is available for the 
ignition of new portions of the gas. If the combustible gas 
is mixed with sufficient air to provide all or nearly all the 
oxygen necessary to burn it, an explosion takes place. This 
is because the combustion spreads almost instantaneously. 



THE RELATION OF COMBUSTION TO HEAT 57 

An enormous quantity of heat is consequently liberated in 
an instant. Gases tend to expand when heated. If they 
are confined within an inclosed space (such as a bottle or 
even a room) , they exert a pressure on the walls of the space 
in consequence of this tendency to expand. If the pressure 
is sufficiently great, the walls of the inclosing vessel or room 
may be shattered. 

When gas has been escaping into a room or oven, there is 
always a possibility that it may be mixed with the air in 
explosive proportions. It is, therefore, extremely dangerous 
to bring a light into the room or near the oven until the gas 
has been shut off and the room or oven well ventilated. 
Vessels containing volatile x liquids such as gasoline and 
benzine are apt to have explosive mixtures in the space above 
the liquid. Such liquids should not be used for cleaning pur- 
poses in a room in which a lamp or fire is burning. Explo- 
sions have been known to occur when benzine was used 
many feet from a flame. 

Finely divided solid or liquid combustibles may also 
form explosive mixtures with air. Explosions of coal dust 
and of flour dust are not uncommon in the air of mines and 
mills. 

Gas and gasoline engines derive their power from the 
explosive combustion of mixtures of air with combustible 
gases and minute droplets of combustible liquids. 

Spontaneous Combustion 

Oxidation of many substances occurs slowly at tem- 
peratures below their ignition points. Phosphorus, for exam- 
ple, oxidizes slowly but completely at ordinary room temper- 
ature, although its ignition point is considerably higher. 
Iron oxidizes slowly in moist air, and, curiously enough, 
combines with more oxygen than when it is burned in pure 

1 A volatile liquid is one which is readily converted into vapor or gas. 



58 ELEMENTARY HOUSEHOLD CHEMISTRY 

or even in compressed oxygen. Linseed oil, exposed to the 
air in thin layers, as when used in paint, oxidizes partially, 
yielding a solid film. The " drying " of paint is due to this 
reaction rather than to the evaporation of any liquid. 

We have learned that when slow oxidations such as these 
occur the quantity of heat set free is the same as if they 
occurred rapidly. Now if the oxidation goes on at such a 
rate that heat is produced a little more rapidly than it is 
conveyed away from the oxidizing body, it is evident that 
the latter will gradually become warmer. This will cause 
the rate of oxidation to become greater ; heat will therefore 
be liberated more rapidly than before ; and the temperature 
of the oxidizing body will continue to go up, until finally 
the ignition temperature is attained and the substance bursts 
into active combustion. Spontaneous combustion has been 
observed in stored coal, in cotton waste wet with oil, in hay, 
and in other materials. 



CHAPTER XI 

FUELS 

Fuels are conveniently classified according to their physi- 
cal state, thus : 

i. Solid Fuels. — Wood, peat, the several varieties of coal, 
charcoal, coke. 

2. Liquid Fuels. — Alcohol, wood alcohol, gasoline, kerosene 
(coal oil), " fuel oil," crude petroleum. 

3. Gaseous Fuels. — Natural gas, coal gas, water gas, producer 
gas, air gas (or gasoline gas) , oil gas, acetylene. 

These all contain carbon, and all but charcoal and coke 
contain hydrogen. Most of them are mixtures of different 
substances, e.g. coal gas of free hydrogen, carbon monoxide, 
and methane (CH4) ; water gas of free hydrogen, carbon 
monoxide, and nitrogen ; etc. The solids and most of 
the gases contain more or less incombustible matter. In the 
gases this consists usually of free nitrogen, free oxygen, 
argon, and carbon dioxide ; in the solids, of oxides and salt- 
like compounds of the metals. The incombustible gases, of 
course, pass up the chimney with the carbon dioxide and 
steam produced in the combustion. The incombustible 
solids, for the most part, remain as ashes, though the smaller 
particles may be swept away into the chimney with the 
gases. 

As the hot gases from a fire cool, the water and some of 
the products of incomplete combustion condense, i.e., change 
from the gaseous to the liquid form, and the minute droplets 
so formed, together with the particles of ash, constitute 
the white matter of smoke. Some of the oily products of 
incomplete combustion which are most easily condensed, 

59 



60 ELEMENTARY HOUSEHOLD CHEMISTRY 

and some of the carbon and ash lodge in the chimney or 
pipes, and the mixture constitutes soot. The oily matter of 
soot, sometimes spoken of as " oil of smoke," is a complex 
mixture of compounds analogous to carbolic acid. 

Solid Fuels 

Wood. — The hard woods are most valued for fuel pur- 
poses. These all come from deciduous trees — trees which 
shed their foliage annually. Those most used as fuel may 
be placed in the following approximate order of merit, 
though it must be remembered that there are many varieties 
of each species and that these have unequal merit : hickory, 
oak, ash, sugar maple, black maple, beech, birch. 

The evergreen conifers and some of the deciduous trees 
yield soft woods, which ignite readily and are therefore 
particularly useful as kindling for harder wood and for coal. 
Soft woods may also be used for fuel proper. The most 
valuable soft-wood fuels are those from the conifers : pine, 
spruce, hemlock, cedar, sequoia, and redwood. 

Wood consists, in the main, of compounds of carbon, 
hydrogen, and oxygen — ■ largely cellulose and closely related 
substances, having an average composition roughly rep- 
resented by the formula, CeHioOs, i.e. C, 44.4 per cent; 
H, 6.2 per cent ; O, 49.4 per cent. 

Mixed with these compounds there is always a considera- 
ble quantity of water and some incombustible " mineral " 
matter, i.e. ash. The conifer woods also contain turpentine 
and resins, consisting of compounds of carbon and hydrogen, 
some of them without any oxygen, some with much less 
oxygen than is contained in the cellulose-like compounds. 
These substances have high heats of combustion, and it is 
their presence which renders the conifer woods more valuable 
for fuel than the soft deciduous woods such as poplar, willow, 
and basswood. 

The amount of water in the wood has a great effect on 



FUELS 6 I 

its practical calorific value, for if much water is present, a 
large proportion of the heat is used in vaporizing (boiling) 
this water. 

The amount of water in the wood depends upon the variety, 
upon the season at which the wood is cut, and upon the 
seasoning. Wood cut in midwinter contains less water than 
that cut at other seasons. No wood is water-free unless it 
has been kiln-dried. But while seasoned wood has only 20 
per cent or less of water, green wood or wet wood may have 
as much as 50 per cent. Green ash contains about 30 per 
cent, green poplar about 50 per cent, of water. It is at least 
partly due to the water contained even in air-dried wood that 
it is impossible to get a very hot fire with wood, except in 
the later stages of the combustion. At that time the water 
and the gases produced by the decomposition have been 
driven off and the fire has become essentially a charcoal fire. 

Weight for weight, there is little difference in the calorific 
value (i.e. heat of combustion) of perfectly dry soft woods 
and perfectly dry hard woods. But wood is bought and 
sold by measure, not by weight. A cord of dry pine — 
a pile 8 feet long, 4 feet wide, and 4 feet high — is said to 
weigh 3000 pounds, and a cord of dry maple from 4500 to 
5000 pounds. Cord for cord, then, dry hard wood has a 
much higher calorific power than soft wood. A cord of hard 
wood yields about the same quantity of heat as a ton of coal, 
viz. 20 to 30 million B. T. U. 

Soft woods, particularly those which are light and porous, 
not only ignite more readily, but also burn more rapidly 
than hard woods. They thus give a hot fire, but one which 
requires constant attention. Hard woods produce more 
charcoal than soft woods, and of a better quality. This is 
another reason why a hard-wood fire is steadier and more 
persistent than one of soft wood. 

The ash from hard wood contains potassium carbonate, 
which in former days was commonly leached out and used 



62 ELEMENTARY HOUSEHOLD CHEMISTRY 

for soap-making and other purposes. Hard- wood ashes have 
considerable value as agricultural fertilizers. This is due 
to the compounds of potassium, phosphorus, and calcium 
contained in them. The potassium compounds are the most 
important in this respect, and since these are soluble in water, 
ashes which have been leached, either intentionally, as in 
the making of lye, or through carelessness, e.g. by exposure 
to rain, have but little fertilizing value. Soft-wood ashes, 
even if protected from leaching, have, as a rule, very little 
value as fertilizers. 

Peat is a substance produced by the decay under water 
of certain swamp plants, particularly mosses. In its natural 
state it contains more water than even green wood. It is 
very difficult to dry below a moisture content of 30 to 50 
per cent, and in this condition its calorific value is little, 
if any, above that of wood. Better drying can, however, 
be accomplished if the fiber is broken up by mechanical 
treatment. Peat improved by such processes of manufacture 
-is now an important fuel in some European countries and is 
beginning to be of importance in Canada. It is admirably 
adapted to domestic use. 

Coal is a general name given to the solid fuels found as 
minerals. There is good evidence that for the most part 
these have been formed by the decay of plants of the conifer, 
fern, and palm families. Under varying conditions there 
have been formed coals showing very material differences in 
composition and physical properties. 

Lignite or brown coal owes its name (from the Latin 
lignum, wood) to the fact that it often shows more or less 
clearly the structure of wood. On account of its propensity 
to break up into powder as it dries, lignite has little com- 
mercial value except in the immediate neighborhood of its 
mines, where it can be used comparatively soon after being 
brought to the surface. There are large deposits of lignite 
in the western regions of the United States and Canada, 



FUELS 63 

but the larger part of the western coals and practically the 
whole of the eastern fuels fall in the following groups. 

Lignitic coal resembles lignite in structure, but is darker 
in color, contains less water, and is more stable. In compo- 
sition and fuel value it is intermediate between true lignite 
and bituminous coal. Most of the coals found in the great 
plains and a considerable part of those found in the far West 
belong to this class. They range from the true lignites, 
containing say 20 per cent of water, down to the lighter 
grades of bituminous coal which contain little or no com- 
bined water. Lignitic coals are valuable fuels. 

Lignitic coal with 18 per cent of water contains about 
50 per cent of carbon, a little less than 5 per cent of hydrogen, 
and 16 per cent of oxygen and nitrogen. It burns with a 
smoky flame and yields from 8000 to 11,000 B.T. U. per 
pound. 

Bituminous or soft coal contains more carbon and much 
less oxygen than lignitic coal, and has, therefore, a higher 
calorific value. Some varieties {e.g. Connellsville) melt 
slightly and cake in burning ; others burn without caking. 
Some burn with little, others {e.g. Nova Scotia) with much, 
flame and smoke. It is from bituminous coal of medium 
grades that coke and coal gas are best manufactured. 
Bituminous coal contains from 55 to 80 per cent of carbon, 
and from 15 to 50 per cent of volatile matter (matter driven 
off as gas in the manufacture of coke). The caking coals 
have usually less oxygen and more volatile matter than 
the non-caking. The surface of a caking coal fire requires 
breaking up occasionally, so as to allow free draft through 
the fire. Bituminous coal is by far the most important fuel 
in North America, if not in the whole world. 

Semi-bituminous or semi-anthracitic coal is intermediate 
between bituminous coal and anthracite. It has over 80 
per cent of carbon and 15 to 20 per cent of volatile matter. 
It burns with a shorter flame than bituminous coal, but may 



64 ELEMENTARY HOUSEHOLD CHEMISTRY 

be either harder or softer. An example of this kind of coal 
is Pocahontas. 

Anthracite or hard coal is the densest and hardest variety 
of coal and contains the most carbon and the least hydrogen, 
oxygen, and volatile matter. It is hard to kindle, burns with 
a steady, intense heat, produces little or no smoke, and 
requires less frequent attention than any of the other varieties. 
Anthracite has from 84 to over 96 per cent of carbon and but 
3 to 10 per cent of volatile matter. 

Good grades of semi-bituminous and anthracite coal yield 
from 13,500 to 15,500 B.T. U. per pound. 

The figures given above for the composition of coals of 
the various classes refer to pure air-dried coals with a mini- 
mum of ash. Commercially, all coals contain considerable 
quantities of dirt and mineral impurity ; and coal as mined 
and shipped always carries some moisture, as distinguished 
from chemically combined water. Perhaps the . average of 
all coals sold would contain 10 to 12 per cent of ash and 
1.5 to 2 per cent of moisture. The amount and character 
of the ash in coal is an important practical consideration. 
In amount it ranges from 3 to 20 per cent, with extremes 
above and below. Coals containing sulphur are more likely 
to give clinkery ashes than sulphur-free coals. Clinkers, 
accumulating upon the grate of a furnace or stove, are objec- 
tionable, not only because they are apt to clog the shaking 
mechanism, but also because they interfere with the draft. 

Coal ashes have much the same composition as clay. 
They have practically no fertilizing value. 

Charcoal is made by the destructive distillation of wood ; 
coke by that of bituminous coal. (See Expts. 24 and 25.) 
They both consist of free carbon mixed with the ash constit- 
uents of the wood or coal from which they are made. Both 
burn without flame (or with a carbon monoxide flame if the 
fire is deep), and both yield about 13,000 B. T. U. per pound. 
Coke is of two kinds: (1) Furnace or metallurgical o>£e,made 



FUELS 65 

in so-called " coke ovens " as a primary product, the gas, 
tar, etc., being secondary products or in all too many cases 
wasted 5(2) Gas coke, a much softer material left in the retorts 
used in the manufacture of illuminating gas from coal. 
Gas coke is a valuable domestic fuel, igniting almost as 
easily as bituminous coal and burning with a very intense 
flameless fire. Furnace coke, on the other hand, is a very 
hard substance and is more difficult to ignite than anthracite. 
While of great industrial importance, this kind of coke is 
unsuitable for domestic use. 

In all solid fuel fires, and especially in coal fires, it is 
important to keep the grate and the surface of the fuel free 
from an accumulation of ashes. Ashes not only impede the 
draft but, covering the surface of the fuel, they prevent 
the oxygen from coming in contact with the combustible 
solid. The shaking of the fire not only clears the grate of 
the ashes which tend to clog it, but also shakes off the cover- 
ing of ashes from the face of the coals and exposes the latter 
to the action of the oxygen. 

For further information about solid fuels the reader is referred to 
Chapter V of Benson's "Industrial Chemistry" (New York, 1913) and 
to the numerous references there cited. 



CHAPTER XII 

FUELS {Continued) 
Liquid Fuels 

The most important liquid fuels are the petroleum prod- 
ucts — especially kerosene. The alcohols are at present 
fuels of secondary importance. 

Petroleum is an oil obtained from underground sources. 
It is a mixture of a great many compounds of carbon and 
hydrogen. In the refining process the more volatile com- 
pounds are separated from those less volatile. A large 
number of products are thus obtained. 

Benzine and gasoline are two of the most useful of the 
light or volatile products ; kerosene is heavier and less 
volatile ; the still less volatile constituents of the crude 
petroleum make up such products as lubricating oils, axle 
greases, vaseline (or petrolatum), and paraffin wax. 

The vapor of benzine and gasoline is given off in sufficient 
abundance at ordinary temperatures to form explosive 
mixtures with air. On account of this danger benzine and 
gasoline should not be used as household fuels. 

Kerosene (called " paraffin " in England and " coal 
oil " in some parts of America), if well made, gives off very 
little vapor at ordinary temperatures — enough to affect 
the sense of smell, but not nearly enough to form an explo- 
sive mixture with air. The momentary application of a 
flame, either above or directly to the surface of the cold oil, 
will cause no ignition. The flame or " flash " test commonly 
applied to kerosene is a test to determine to what temperature 
the oil must be heated in order that it may give off sufficient 

66 



FUELS 



6 7 




Fig. 33. 



A blue flame kerosene 
stove. 



vapor to form a combustible mixture with air. The laws of 
most countries prescribe a minimum flash point for oils 
offered for sale for illuminating purposes. 

Kerosene stoves are of two types. One type is con- 
structed like a large kerosene lamp and gives a yellow, sooty 
flame. The other type gives a 
blue flame like a Bunsen burner. 
In the lamp-like stove the oil 
rises from the reservoir to the 
burner through a wick, and is 
converted into gas in the flame 
itself. In the blue-flame stoves 
the oil is vaporized and mixed 
with air before it reaches the 
flame. The latter type is prac- 
tically a combined gas factory 
and Bunsen burner. Figure 33 
shows such a stove. 

Wood alcohol and " denatured " grain alcohol are con- 
venient household fuels for small fires, such as those of 
chafing dishes, table kettles, and coffee percolators. Wood 
alcohol (methyl alcohol) is a product of the destructive dis- 
tillation of wood (see Expt. 24, p. 41), and therefore a by- 
product of the charcoal industry. Grain alcohol (ethyl 
alcohol) is produced by the fermentation of sugars. The 
reason it is called " grain " alcohol is that it is so often made 
by converting the starch of grain, such as corn or rye, into 
sugar, by the action of malt, and fermenting the sugar so 
obtained. But it is also made from molasses and from 
potatoes. Ethyl alcohol is the active, intoxicating principle 
of all fermented and distilled beverages. Denatured alcohol 
is ethyl alcohol to which some substance has been added to 
render it unpalatable. Methylated spirits is a common 
variety of denatured alcohol. It is grain alcohol to which a 
small proportion (about 10 per cent) of wood alcohol and 



68 ELEMENTARY HOUSEHOLD CHEMISTRY 

usually a small proportion of some other substance, such as 
benzine, has been added. 

Both wood alcohol and grain alcohol contain the three 
elements, carbon, hydrogen, and oxygen. Both liquids 
are readily ignited and burn with smokeless flames. 

Three quarts of grain alcohol, or of methylated spirits, 
will give nearly as much heat as four quarts of wood alcohol. 

The present importance of the alcohols as fuels is, as 
already stated, a secondary one. This is due to their rela- 
tively high price as compared with the petroleum products. 
The quantity of these two alcohols which could be produced 
from agricultural products is practically unlimited, and it is 
possible that some day these substances may find more use 
as fuels than they do at present. 

Gaseous Fuels 

The gases most used in the household for fuel purposes are 
natural gas, coal gas, water gas, and gasoline or ■" air " gas. 

Natural gas exists underground in certain localities, 
usually in porous strata, whence it is obtained by boring wells. 
It consists of the compound methane, CH 4 , mixed with small 
quantities of other gases. Used with suitable burners it 
is the most convenient and most efficient of all the natural 
fuels. It yields about iooo B. T. U. per cubic foot. Natural 
gas is supplied to many of the cities of Pennsylvania, Ohio, 
Indiana, and western New York. In Canada it occurs in 
New Brunswick, Alberta, and other places. 

Coal gas, made by the destructive distillation of bituminous 
coal, constitutes the gas supply of most European and of 
many American cities. The coal is heated in closed retorts, 
the gases produced being conducted off through pipes. 
The gases are purified by cooling, washing with water, and 
passing through lime or iron oxide. The by-products are 
gas coke, which remains in the retort ; coal tar, which con- 



FUELS 



6 9 



denses from the gases on cooling, and from which numerous 
useful compounds are manufactured — antiseptics (such as 
carbolic acid), dyes (see Chapter XLIII), etc. ; and am- 
monia, which remains in the wash water (see Chapter XXIII). 
The lime and iron oxide remove the sulphur compounds from 
the gas. 

The chief constituents of coal gas are free hydrogen and 
methane, each of these being present to the extent of about 




Fig. 34. — A gas stove. 

40 per cent. In addition to these two main constituents 
there are carbon monoxide (usually 6 to 8 per cent) and some 
compounds of carbon and hydrogen, other than methane. 
It is these latter hydrocarbons which make the gas burn with 
a luminous flame. To obtain a flame which will not deposit 
soot, burners on the principle of the Bunsen burner are used. 
In such burners the gas is mixed with air before ignition. 
Coal gas yields 600-625 B. T. U. per cubic foot. A ton of 
coal yields about 10,000 cubic feet of gas, which contain 
only about one fifth of the original fuel value of the ton of 
coal. 

Water gas is used in many American cities. It is prepared 
by passing steam through white-hot coke or anthracite coal. 
The chief constituents of water gas are carbon monoxide and 
hydrogen. Gas made from coke contains about 45 per 
cent of each of these two gases, the remaining 10 per cent 
being methane, carbon dioxide, free nitrogen, and free oxygen. 



70 ELEMENTARY HOUSEHOLD CHEMISTRY 

Gas made from anthracite has a higher proportion of these 
minor constituents — about 20 per cent instead of 10. 

Consisting largely of carbon monoxide, water gas is 
extremely poisonous — much more so than coal gas. The 
smallest leakage of water gas from pipes or cocks is therefore 
a serious matter. Water gas has from 40 to 60 per cent of the 
fuel value of the coal or coke from which it is made. It 
yields about 350 B.T. U. per cubic foot, but the fuel value is 
frequently increased by enrichment. (See below.) 

Water gas burns with a blue flame, which has very low 
illuminating power. In order to make it into an illuminating 
gas for use with old-style burners, it is common to mix with 
it a gas made by heating petroleum oils to a high temperature. 
(See "Oil gas," p. 77.) This process is called enriching 
the gas. Enriched water gas may have a fuel value as high 
as 700 B. T. U. per cubic foot. In many cities a mixture of 
coal gas and water gas is used. 

Gasoline gas (" air " gas) is made chiefly in private 
plants for the supply of rural homes or of institutions situated 
at a distance from a city supply. It is a mixture of gasoline 
vapor and air. Gasoline consists of the more volatile hydro- 
carbons of petroleum. The gas is made from it by exposing 
the liquid on folds of canvas to a current of air. The gasoline 
evaporates, the vapors mixing with the air, the supply of 
which is so regulated that the hydrocarbons will not become 
liquid again in the pipes. The gasoline gas burns with a 
luminous (and therefore sooty) flame, but a blue flame is 
obtained by admitting additional air at the burner, which 
must be of the Bunsen type. 

Compressed and Liquefied Gas. — When the gas mixtures 
used for fuel purposes, such as coal gas or oil gas, are subjected 
to great pressure, some of the constituents (hydrocarbons 
containing a large proportion of carbon) liquefy. This liq- 
uefied portion of the gas may be separated from the por- 
tion which remains in the gaseous condition, and the latter 



FUELS 71 

may be stored in cylinders in its compressed state and shipped 
to houses or institutions which are not supplied with gas 
through pipes. 

A German chemist, named Hermann Blau, has patented 
a process in which some of the constituents of oil gas are 
liquefied and removed, then the remaining gases are com- 
pressed to a liquid condition. Blau gas is used more for 
lighting than for cooking purposes. 

Surface Combustion 

Gas burners have recently been designed which render it 
possible to mix the gas with exactly sufficient air for its com- 
plete combustion and to cause the mixture to burn flame- 
lessly in a pile of granular incombustible material, such as 
pieces of silica, SiC>2, or alumina, AI2O3. Combustion of gas 
so conducted is termed surface combustion. Surface com- 
bustion is very economical because (1) it avoids the heating 
of air not used in the combustion, and (2) heat radiated from 
the incandescent pile of refractory material is more penetra- 
tive than heat from a gas flame. It is claimed that surface 
combustion gas stoves, doing the same work as stoves of 
the ordinary Bunsen type, will use 35 to 45 per cent less gas 
than the Bunsens. 

Further information on liquid and gaseous fuels, including numerous 
references to the literature of the subject, will be found in Chapter VI 
of Benson's "Industrial Chemistry" (New York, 1913). For a prac- 
tical method of comparing the values of the common household fuels, 
the reader is referred to Lynde's "Physics of the Household" (New 
York, 1914), pages 152-153. 



CHAPTER XIII 

LIGHT AND ILLUMINANTS 

Experiment 36.* 

Materials : 

Platinum wire, 2 or 3 inches. 

Iron wire, same gauge and length. 

Magnesium ribbon, ^ inch. 

Quicklime, small lump, say, §-inch cube. 

Crucible tongs or forceps. 

Blowpipe. 

(a) With the tongs hold in a Bunsen flame side by side a piece 
of iron wire and a piece of platinum wire. Note the gradual 
changes of color as the temperature of the wires rises. 

(b) Hold a piece of magnesium wire in the tongs, and ignite 
it with the Bunsen flame. Note the white light emitted as the 
magnesium burns. (This is the light used in making flashlight 
photographs.) 

The ash, which remains after the combustion of the magnesium 
and which retains something of the form of the original ribbon, is 
magnesium oxide (sometimes called magnesia). Bring this ash 
again into the flame and note the change of color it undergoes as 
it is heated. Blow into the flame with the blowpipe, directing 
a gentle current of the flowing gases towards the magnesia. Does 
it become brighter? Is its color altered? (c) Hold a piece of 
lime in the flame a little above the inner cone. Note its color. 
Blow the flame upon it with the blowpipe. Does the color change ? 
If an oxyhydrogen blowpipe is available, direct its flame against 
the lime. Is more light now emitted ? What is its color? 

When substances are heated to a sufficiently high tem- 
perature, they give out light. They are then said to be in an 
incandescent condition. Like heat, light is a form of energy, 
and incandescence is due to a transformation of some of the 
heat into light. 

72 



LIGHT AND ILLUMINANTS 



73 



Gases can be heated to incandescence, and the colors of 
the light they then give out are characteristic of the various 
substances. Each gaseous compound yields its own color, 
unless when heated to in- 
candescence it is decom- 
posed, in which event it 
gives the colors of its decom- 
position products. 

To obtain the characteristic colors of gases, a glass tube 
provided with metal electrodes (see Fig. 35) is first filled with 
the gas. Then most of the gas is pumped out and the tube 
is sealed by melting the glass. On passing the electric dis- 
charge (spark) from an induction coil through the gas from 



Fig. 35. — A form of tube in which gases 
are electrically heated to incandescence. 




Fig. 36. — Bunsen and Kirchhoffs Spectroscope. An instrument 
used in the analysis of light. 



electrode to electrode the characteristic light appears. The 
color of the light may be analyzed by means of an instrument 
called a spectroscope. 

It was by the color of its light that the element helium was 



74 ELEMENTARY HOUSEHOLD CHEMISTRY 

discovered in the sun's atmosphere many years before it was 
found upon our planet ; and it was from observations of light 
color that astronomers inferred that the tail of Halley's comet 
(visible in 1910) contained cyanogen gas (C 2 N 2 ). Incan- 
descent sodium vapor emits yellow light ; potassium, violet ; 
calcium, red; barium and copper, green, etc.; and most com- 
pounds of these metals when heated in a Bunsen flame impart 
to it these characteristic colors. 

Experiment 37.* 

Materials : 

Small portions of the chlorides of sodium, potassium, calcium, 

strontium, and barium. 
Platinum wires sealed in glass handles and carefully cleaned 
by alternate heating in Bunsen flame and dipping in pure 
concentrated hydrochloric acid until they do not color the 
flame. 
Heat a clean platinum wire and dip it while hot into one of the 
salts, then bring again into the Bunsen flame and note the color 
imparted to it. Repeat with the other salts, using a thoroughly 
clean wire in each instance. 

In practical illumination, however, the incandescence of 
solids is of much more importance than that of gases. The 
color of the light emitted by an incandescent solid depends 
not only on what substance the solid is, but also on the tem- 
perature to which it is heated. As the temperature of any 
solid is gradually raised, red light is first emitted, then the 
other colors of the rainbow are successively combined with the 
red until finally white light (which is composed of all the rain- 
bow colors) is given out. The terms commonly used to dis- 
tinguish high temperatures are said to correspond roughly to 
the following points on the Centigrade and Fahrenheit scales : 

Incipient red heat 525 C. or 1000 F. 

Dull red heat 700 C. or 1300 F. 

Bright red heat 950 C. or 1750 F. 

Yellow heat 1100 C. or 2000 F. 

White heat 1500 C. or 2700 F. 



LIGHT AND ILLUMINANTS 75 

Substances which radiate heat badly are more readily heated 
to high temperatures than good heat radiators. This fact 
is taken advantage of in " gas mantle " lighting (see p. 78). 

Experiment 38. 

Materials: 

Candle. 

Kerosene lamp. 

Porcelain dish or piece of broken porcelain. 
Hold a cold piece of porcelain in the flame of (1) a candle, (2) a 
kerosene lamp, (3) a luminous gas flame. 

Candles and Lamps 

In the more primitive methods of lighting — the candle, 
the gas light, and the oil lamp — the light is given off by 
the particles of carbon which are formed by the decomposi- 
tion of some of the hydrocarbon gases of the flame. For the 
heat of the flame not only changes the liquid oil or the solid 
candle into gases, but decomposes these gases into simpler 
constituents, one of which is carbon. Lampblack is manu- 
factured by cooling the luminous flame of pine knots, crude 
petroleum, or natural gas, by means of a metal plate or re- 
volving drum, or by burning such substances in a limited 
draft of air and conducting the smoke into settling cham- 
bers. Where such flames are used for lighting purposes the 
supply of air must be sufficient to cause the carbon to burn 
completely in the outer layers of the flame. One great ad- 
vantage of a lamp over an open flame is that the chimney 
promotes an upward draft of air around the flame and thus 
permits the fuel to be supplied to the flame at a rate which 
would cause smoking in an open flame. As air is supplied 
more rapidly to the flame the fuel gases can also be more 
rapidly supplied. The result is a brighter, more intense 
light. It is possible, however, as every one knows, to supply 
fuel too rapidly to a lamp flame — by turning up too much 



76 ELEMENTARY HOUSEHOLD CHEMISTRY 

of the wick. This causes smoking in the lamp, with conse- 
quent deposition of soot on the chimney. 

Candles were formerly made of tallow. The materials 
now commonly used for the cheaper kinds of candles are (i) 
paraffin and (2) a mixture of solid acids made from animal 
or vegetable fats and known commercially as " stearin" 
Wax and spermaceti candles are more expensive. The wax 
most used is beeswax bleached by sunlight ; spermaceti is a 
wax obtained from the sperm whale. Mixtures of these 
various materials are sometimes used, — spermaceti and 
stearin, etc. 

The earliest lamps burned vegetable and animal fatty oils, 
such as olive oil, lard oil, and whale oil. Lamps for petroleum 
oils were first made about 1853, an d after the discovery of 
petroleum in Pennsylvania (1859) they quickly replaced the 
older forms. To-day kerosene is the universal lamp fuel in 
America. Its one disadvantage, as compared with the fatty 
.oils previously used, lies in the possibility of explosions. 
Much ingenuity has been expended upon the construction 
of lamps, and the best types now on the market can be 
used with little risk, provided they are kept in good con- 
dition. Explosions can only occur when the bowl of the 
lamp contains a mixture of oil vapor and air in explosive 
proportions, and when that mixture is ignited. Ignition of 
the mixture may occur either through the wick being turned 
down so far that the lighted portion comes in contact with 
the gas in the bowl, or through a portion of the explosive 
mixture reaching the flame, or vice versa. 

The danger of explosion may be lessened by (1) keeping 
the lamp clean — free from charred wick, oil, and dirt of 
all kinds 5(2) keeping the bowl well filled, so as to lessen the 
space available for the accumulation of explosive gas; (3) 
using only a loosely plaited, soft, long-staple cotton wick, 
and soaking it in oil before lighting it the first time; (4) avoid- 
ing moving the lamp, and (in case it must be moved) carrying 



LIGHT AND ILLUMINANTS 77 

it steadily so as not to shake up the oil ; (5) putting out the 
light by means of an extinguisher, or, if the lamp be not pro- 
vided with one, turning down the wick until the flame flickers, 
and then blowing a sharp puff of breath across the top of the 
chimney, but not down it. 

Lamps with side fillers should not be purchased. If they 
are in use, the side fillers should be kept well closed. Of 
course, oil should never be poured into the bowl of a lighted 
lamp. Lamps with the wick tube well extended down into 
the bowl, or prolonged into a wire-gauze wick mantle, are 
safer than those without such an appliance. Lamps with 
metal bowls are much safer than those with glass bowls. 
It is only rarely that a glass bowl is shattered by an explosion, 
but the alarm caused by the explosion is apt to result in the 
lamp being dropped, in which case the glass bowl is apt to 
be broken and the oil ignited. Wicks should be long enough 
to trail on the bottom of the bowl for about two inches. 
When this two inches is burned off, the wick should be 
renewed. 

Gas Lights 

The older methods of gas lighting depend on the same 
principle as the candle and kerosene lights. Carbon is 
liberated within the flame and heated to incandescence. 
The amount of light obtained depends on (1) the number of 
carbon particles liberated and (2) the temperature to which 
they are heated. Coal gas and gasoline gas (see p. 70) con- 
tain sufficient of the so-called higher hydrocarbons — those 
containing a higher proportion of carbon than does methane 
— to give luminous flames. So also do " oil " gas and acety- 
lene gas. 

Oil gas is made from certain heavy oils ; for instance, some 
of the heavier petroleum products. The oils are vaporized 
by heating and the vapors then subjected to a still higher 
temperature (1800 F.). The heavy molecules of the oils 



78 ELEMENTARY HOUSEHOLD CHEMISTRY 

are thus decomposed into the smaller molecules of substances 
which remain gaseous at ordinary temperatures. The pro- 
cess is known technically as " cracking." Oil gas is often 
compressed into cylinders for transportation. It has been 
and is still much used for lighting railway cars. It requires 
a special form of burner. 

Acetylene gas differs from other illuminating gases in 
consisting, not of a mixture, but of a single chemical com- 
pound, C 2 H 2 . It is formed by the action of water on calcium 
carbide, CaC2, a substance made in the electric furnace from 
lime and coke. The reaction occurring in an acetylene gener- 
ator is the following : 

CaC 2 + 2 H 2 = Ca (OH) 2 + C 2 H 2 

Calcium carbide + Water = Slaked lime + Acetylene 

It requires a special form of burner, but gives a brilliant 
white light. Its great disadvantage is its explosiveness. 
Not only does it form explosive mixtures with air, but in a 
'compressed state it is itself explosive. Although acetylene 
was at first used exclusively for lighting purposes, it is now 
used also for cooking and heating. 

Natural gas and water gas do not burn with sufficiently 
luminous flames for illuminating purposes. They are, how- 
ever, rendered suitable for such purposes by adding to them 
a suitable quantity of the " higher hydrocarbons." This 
may be added in the form of light petroleum oils, such as 
benzine, or in the form of oil gas. (See p. 70.) 

Gas Mantles 

Another device much used to obtain light from flames 
which otherwise are non-luminous is to suspend in them an 
incombustible solid capable of converting a part of the heat 
of the flame into light. The first substance used success- 
fully for this purpose was lime. To obtain light from lime 
a very high temperature is necessary, as the light obtained 



LIGHT AND ILLUMINANTS 79 

is white. A small quantity of fine lime powder can be 
heated, to the requisite temperature by the heat of an alcohol 
burner (spirit lamp). To heat a large pencil of lime, how- 
ever, it is necessary to supply undiluted oxygen to a flame 
of hydrogen or of one of the commercial illuminating gases. 
The oxyhydrogen limelight has been much used in pro- 
jecting lanterns, and we owe the familiar phrase " to stand 
in the limelight " to the use of such lanterns in the theater. 
At the present time the limelight has been largely super- 
seded for such purposes by the electric arc light. 

The success of the limelight prompted many attempts 
to find other incombustible and infusible substances which 
could be used to convert some of the heat of non-luminous 
flames into light. The " mantle " invented by Auer von 
Welsbach represents the result of the most successful of these 
attempts. This mantle consists of a mixture of the oxides 
of two of the rarer metals — thorium and cerium. The mix- 
ture which gives the best results is composed of i part of 
cerium oxide to 99 parts of thorium oxide. A fabric of ramie 
or mercerized cotton is made into the form of the desired 
mantle, and is sewed with asbestos thread. This mantle 
of textile fabric is then soaked in a solution of the nitrates 
of the metals. When the mantle is " burned off," the or- 
ganic matter is oxidized and passes off. At the same time 
the nitrates are decomposed, yielding gases (which pass off) 
and the oxides, which remain as an ash, retaining the form 
of the original fabric. The flame used to heat these mantles 
is a Bunsen flame. For the same amount of gas burned 
these incandescent burners give 6 to 8 times as much light 
as the best of the old flat-flame burners, and 5 to 6 times 
as much light as the round flame (Argand) burners, which 
depended for their luminosity on the incandescence of lib- 
erated carbon. 



80 ELEMENTARY HOUSEHOLD CHEMISTRY 

Electric Lighting 

There are two processes of electric lighting, viz. the arc 
and the incandescent^ electric light. As the former is used 
only for lighting streets and large buildings it need not be 
considered here. 

In the most common forms of incandescent electric light 
a filament of carbon or a wire of some metal, such as tungsten 
or tantalum, is heated to incandescence by means of an elec- 
tric current. As the filament or wire is enclosed in a glass 
bulb from which the air has been pumped out, no combustion 
occurs. The light and heat produced come directly from the 
electric energy of the current. Incandescent electric lights, 
therefore, neither use up the oxygen of the house air nor give 
off any products of combustion nor any leakage products 
to contaminate the air. 

Electric lights are more conveniently lighted and extin- 
guished, and are less dangerous than any of the other forms 
of light. They require less attention than incandescent gas 
lights and much less than lamps or candles. 

Filament lamps, particularly those of carbon, deteriorate 
in use. Some of the material of the filament vaporizes and 
condenses on the inner surface of the glass. This both dark- 
ens the glass and weakens the filament. The " burning- 
out " of lamps is due to the breaking of the filament. It is 
usually economical to discard a lamp before the filament 
becomes thin enough to break, because, as the filament de- 
teriorates, the light-giving power of the lamp is greatly di- 
minished. When the light becomes reddish in color, the 
lamp should be replaced by a new one. 

The metallic filament lamps commonly made at the present 
time use only about one third the current used by carbon 
lamps of the same candle power, that is to say, of the same 
light-giving power. The earlier tungsten filaments were 
very fragile, and the lamps had to be handled much more 



LIGHT AND ILLUMINANTS 8 1 

carefully than carbon lamps. But means have been found 
of making stronger tungsten filaments, and the best modern 
ones are sufficiently strong for most purposes. Metallic 
filaments are stronger when hot than when cold. In dusting 
or cleaning lamps of this type the current should be turned 
on during the operation. 

Carbon filaments and tungsten filaments last about the 
same length of time. They average about iooo hours of 
actual lighting, or about one year's ordinary household 
service. 

For discussion of the physical properties of light with special reference 
to the household the reader is referred to pages 246-273 of Lynde's 
"Physics of the Household" (New York, 1914). 



CHAPTER XIV 

x 

ACIDS AND SALTS 

The following experiments are designed to show what 
common characteristics the substances called acids have, 
and to illustrate the relations existing among acids, metals, 
and the substances called salts. 

Experiment 39. 

Materials : 

Tartaric acid, a few crystals. 

Citric acid, a few crystals. 

Magnesium ribbon, 6 or 8 pieces, \ inch long. 

Copper foil, 2 pieces, \ inch X \ inch. 

Zinc foil, half a dozen pieces, 1 inch X 2 inch. 

1. Label six test tubes and fill them with distilled water. Into 
-them put respectively: 

(1) One or two drops concentrated sulphuric acid. 

(2) One or two drops concentrated hydrochloric acid. 

(3) Five to ten drops reagent acetic acid. 

(4) A few crystals tartaric acid. 

(5) A few crystals citric acid. 

(6) Nothing. 

2. Shake each tube to mix the contents. Use them for the 
following experiments : 

(a) Taste each. What similarity of taste do you observe in 
the tubes to which acid was added ? 

(b) Test each with blue litmus paper. 

(c) Pour out a small portion of each into another test tube and 
add a piece of magnesium ribbon. Describe and explain what 
occurs. What three characteristics are common to the acids 
tested ? 

Experiment 40. 

Materials : 

Acid solutions prepared for Experiment 39. 
Copper foil, 2 pieces, | inch X \ inch. 

82 



ACIDS AND SALTS 83 

Zinc foil, 4 pieces, 1 inch x 2 inch. 
Iron fillings. 

To what class of elements do the four substances, magnesium, 
zinc, iron, and copper, of which you have specimens, belong? 
What properties are common to the four ? 

To discover whether zinc and iron are acted upon by acids as 
the magnesium was, place two portions of each in separate test 
tubes and add a little of any two of the acid solutions prepared 
for Experiment 39. 

Test copper in the same way. Also heat concentrated hydro- 
chloric acid till it just begins to boil, remove from flame, and when 
boiling ceases, add a piece of copper foil. 

From your experiments infer whether every acid acts on every 
metal. 

Experiment 41. 

Materials : 

Magnesium ribbon in pieces of about 0.25 gram. 
Zinc foil, i inch X \ inch. 
To discover what products are formed by the action of acids 
on metals make the following experiments : 

(a) Place a piece of magnesium ribbon in a test tube and pour 
in enough dilute sulphuric acid to cover it. Keep the mouth of 
the tube covered with the thumb for a minute or two ; then, bring- 
ing the flame of a burner or match to the mouth of the tube, 
remove the thumb. If no effect is noted, keep the tube closed 
for a longer time and then apply the flame again. Add a little 
more magnesium and set the tube aside for Experiment (d) . 

(b) Treat magnesium with dilute hydrochloric acid, testing the 
gas evolved as in (a). 

(c) Treat zinc with dilute sulphuric or dilute hydrochloric acid 
and test the gas evolved as in (a). 

(d) Filter off any magnesium left undissolved in (a), collecting 
the filtrate (liquid which runs through the filter) in a dish. Evap- 
orate this filtrate to dryness under the hood. Examine what 
remains in the dish. 

What gas is produced by the action of an acid on a metal? Is 
this gas an element? From which of the reagents (substances 
entering into the chemical change) is this gas derived? Can it 
be from the metal? From the water? Recall experiment with 
magnesium and water without acid. What element is common to 
all acids? 



84 ELEMENTARY HOUSEHOLD CHEMISTRY 

Experiment 42.* 

Materials : 

Sodium in small pieces under oil. 
Alcohol. 
Ether. 
Apparatus : 

Forceps to handle the sodium. 
Filter paper. 
(Where this experiment is made for demonstration purposes 
the use of a filter pump is recommended.) 

In an evaporating dish under the hood place a little concentrated 
hydrochloric acid. Cut sodium into pieces smaller than a pea, 
dry them with filter paper, and add one by one to the hydrochlo- 
ric acid. What gas is given off? (See Expt. 41.) Note what 
forms in the acid. Filter, wash with alcohol, then with ether, 
allow to dry, and taste. What familiar substance is the product 
of the action of hydrochloric acid on sodium? This substance 
lends its name to the class of solid substances produced by the 
interaction of metals and acids. 

There is a large class of compounds of hydrogen having 
the following characteristics in common : 

(1) They taste sour. 

(2) Their aqueous solutions turn blue litmus 1 red. 

(3) They react with many metals, setting hydrogen free. 

Compounds of this class are known as acids. A few of 
the acids contain only one other element combined with their 
hydrogen. Thus, hydrochloric acid (called also muriatic 
acid) is simply hydrogen chloride, HC1 ; and hydrofluoric 
acid, simply hydrogen fluoride, HF. 

The majority contain some oxygen. Thus, sulphuric 
acid, H2SO4, contains hydrogen, sulphur, and oxygen ; nitric 
acid, HNO3, contains hydrogen, nitrogen, and oxygen. The 
organic acids, of which there are a great many, always con- 
tain carbon, hydrogen, and oxygen. The sour taste of fruits 

1 Litmus is a coloring matter derived from lichens found on trees and cliffs 
on the sea coasts of Europe. 



ACIDS AND SALTS 85 

is due to organic acids. The chief acid of grapes is tartaric, 
H2C4H4O6 ; of apples, pears, and mountain ash berries, malic, 
H2C4H4O5 ; of lemons, oranges, gooseberries, cranberries, 
and currants, citric, H3C6H5O7. Vinegar owes its sourness 
to acetic acid, HC2H3O2. Sour milk contains lactic acid, 
HC3H5O3, and rancid butter, butyric acid, HC 4 H 7 2 . 

Salts 

Whenever an acid acts upon a metal, not only is hydrogen 
set free, but there is produced also a compound belonging to 
the class known as salts. In the majority of cases, if water is 
present, the salt is left in solution in the water. Thus : 

Sodium with hydrochloric acid yields hydrogen and com- 
mon salt {sodium chloride). 

Zinc with sulphuric acid yield hydrogen and zinc sul- 
phate. 

Magnesium with acetic acid yields hydrogen and mag- 
nesium acetate. 

In general terms, then, we may write : 

Metal + Acid = Salt + Hydrogen 
The salt is composed of the metal and the elements of the 

acid other than the hydrogen set free. 

Thus, common salt is a compound of sodium with the 

chlorine of the hydrochloric acid ; zinc sulphate, a compound 

of zinc with the sulphur and oxygen of the sulphuric acid; 

and magnesium acetate a compound of magnesium with the 

carbon, oxygen, and three fourths of the hydrogen of acetic 

acid. 
This may perhaps be made clearer by writing the equations 

for the above reactions : 



Metal 


+ 


Acid = 


Salt + 


Hydrogen 


2 Na 


+ 


2 HC1 


2 NaCl + 


H 2 


Zn 


+ 


H 2 S0 4 


ZnS0 4 + 


H 2 


Mg 


+ 


H 2 S0 4 


MgS0 4 + 


H 2 


Mg 


+ 


2 HC 2 H 3 2 = 


Mg (C 2 H 3 2 ) 2 + 


H 2 



86 ELEMENTARY HOUSEHOLD CHEMISTRY 



Acid Radicles 

The common constituent of the acid and salt — the CI, the 
S0 4 , and the C2H3O2 — is known as the acid radicle. 1 It does 
not exist as a separate substance, but is present in the acid 
and all its salts. Thus, the acid may be regarded as a com- 
pound of the radicle with hydrogen, and the salts as com- 
pounds of the radicle with metals. The formulas of radicles 
customarily include one or more dashes representing the 
bonds that join the radicles to the hydrogen or metal. Thus : 

—CI, =S0 4 , — C2H3O2 

Definitions of Acid and Salt 

An acid may be defined as a substance containing hydrogen, 
replaceable by a metal, and a salt as a compound derived from 
an acid by the replacement of hydrogen by a metal. 

Nomenclature of Salts 

It will be noted that, as a rule, the name of the salt is 
obtained from that of the acid by substituting the suffix -ate 
for the suffix -ic. Thus, the salts of nitric acid are nitrates, 
those of acetic acid, acetates, etc. An important exception is 
hydrochloric acid, whose salts, being compounds of metals 
and chlorine, are called chlorides. Thus, NaCl, Sodium 
chloride ; FeCl 3 , Iron chloride ; etc. 

Notation 

The formulas of acids and salts are always so written as 
to indicate clearly what acid radicle they contain. For 
example, the formulas of all nitrates have the nitrate radical, 
— N0 3 . We therefore write the formula of calcium nitrate 

1 Also spelled radical. 



ACIDS AND SALTS 87 

Ca(N0s)2, rather than CaN 2 6 ; and that of aluminium sul- 
phate AI2 (S0 4 )3, rather than Al 2 S 3 0i 2 . For the same reason, 
in writing the formulas of the organic acids, the replaceable 
hydrogen atoms are written separately from the hydrogen 
atoms which form a part of the radicles. Thus, tartaric acid, 
H2C4H4O6, not H 6 C 4 6 ; and acetic acid, HC 2 H 3 2 , not 
H4C 2 2 . 

Valence 

When sodium or potassium or silver replaces the hydrogen 
of an acid, one atom of the metal is regarded as having re- 
placed each atom of hydrogen driven out of the molecule. 
Thus nitric acid, HN0 3 , yields the salts NaN0 3 , KN0 3 , and 
AgNOs; sulphuric acid, H 2 SC>4, the salts Na 2 S0 4 , K 2 S04, and 
Ag 2 S0 4 ; and phosphoric acid, H3PO4, the salts Na 3 P0 4 , 
K3PO4, and Ag3P04. But the magnesium and calcium atoms 
are regarded as having each the power of replacing two 
atoms of hydrogen. We have therefore for the nitrates of 
these metals the formulas Mg(N03) 2 and Ca(N03) 2 ; for the 
sulphates MgSC>4 and CaS0 4 ; and for the phosphates 
Mg 3 (P0 4 ) 2 and Ca3(P0 4 ) 2 . In the magnesium nitrate the 
atom of magnesium has replaced the hydrogen atoms in 
two molecules of the acid ; in the sulphate it has replaced 
the two atoms of the sulphuric acid molecule, H 2 S0 4 ; in the 
phosphate three atoms of magnesium have replaced the six 
atoms of hydrogen in two molecules of phosphoric acid. 

The aluminium atom replaces three atoms of hydrogen. 
The formulas of aluminium nitrate, sulphate, and phosphate 
are, therefore, A1(N0 3 ) 3 , A1 2 (S0 4 ) 3 , and A1P0 4 . 

The valence of a metal is the number of atoms of hydrogen 
which its atom will replace. 

Thus, sodium, potassium, and silver have a valence of one. 
These metals are said to be univalent. 

Magnesium and calcium have a valence of two. They are, 
therefore, called bivalent metals. 



88 ELEMENTARY HOUSEHOLD CHEMISTRY 

Aluminium has a valence of three. It is trivalent. 

Some metals have one valence in one set of compounds and 
another valence in another set. Thus, iron in ferrous oxide, 
FeO, ferrous chloride, FeCl 2 , and ferrous sulphate, FeS0 4 , 
is bivalent ; but in ferric oxide, Fe 2 3 , ferric chloride, FeCl 3 , 
and ferric sulphate, Fe 2 (S0 4 ) 3 , it is trivalent. Mercury in 
mercurous chloride (calomel), HgCl, is univalent; in mer- 
curic chloride (corrosive sublimate), HgCl 2 , it is bivalent. 

The term valence is also used with reference to the non- 
metallic elements. Thus oxygen is said to be bivalent because 
its atom combines with two atoms of hydrogen, forming 
H 2 0; and chlorine is univalent in many of its compounds, 
such as HC1 and its salts, KC1, NaCl, CaCl 2 , etc. 

The acid radicles, — CI, — N0 3 , and — C 2 H 3 2 , may also 
be said to be univalent ; = SO4, = C0 3 , = C2O4, etc. to be 
bivalent ; and = PO4, to be trivalent. 

Acid Salts 

Acids whose molecules have more than one atom of re- 
placeable hydrogen may form compounds in which only a 
part of the replaceable hydrogen is actually replaced by a 
metal. Thus if half the hydrogen of sulphuric acid is re- 
placed by sodium, we have NaHS0 4 ; when one third of the 
hydrogen of phosphoric acid is replaced by potassium, we have 
KH 2 P0 4 ; and when two thirds of the hydrogen of phosphoric 
acid is replaced by potassium, we have K 2 HP0 4 . 

These compounds come within our definition of salts be- 
cause they are formed from acids by replacement of hydro- 
gen by metals. But they also come within our definition of 
acids because they contain hydrogen replaceable by metals. 
They are therefore called acid salts. Among the important 
acid salts we have : 

Acid sodium carbonate, more commonly called sodium 
bicarbonate, or baking soda, NaHC0 3 . 

Acid sodium sulphate or sodium bisulphate, NaHS0 4 . 



ACIDS AND SALTS 89 

Acid potassium sulphate or potassium bisulphate, KHSO4. 

Acid potassium oxalate, potassium binoxalate, " salt of 
sorrel " or " salt of lemons," KHC 2 4 . 

Acid potassium tartrate, potassium bitartrate or " cream 
of tartar," KHC 4 H 4 6 . 

Disodium phosphate, Na2HP0 4 . This is the most common 
phosphate of sodium and is often called simply sodium phos- 
phate. 

Monocalcium phosphate, acid phosphate of lime, Ca(H 2 P0 4 )2 
or CaH 4 (P0 4 ) 2 . 

EXERCISES 

1. Write the formulas and names of the acids corresponding 
to the salts whose formulas follow: 

(1) NaN0 3 (2) KNO2 (3) MgS0 3 (4) MgS0 4 

(5) HgCl 2 (6) HgCl (7) FeCl 2 (8) FeCl 3 

(o)AgCl (io)Ag 2 S0 4 (11) A1 2 (S0 4 ) 3 (i 2 )A1P0 4 

2. Give the valences of the metals in Exercise 1. 

3. Write the names of : 

(1) The sodium salt of nitric acid. 

(2) The calcium salt of sulphuric acid. 

(3) The silver salt of hydrochloric acid. 

(4) The magnesium salt of malic acid. 

(5) The potassium salt of nitrous acid. 

(6) The sodium salt of carbonic acid. 

(7) The two iron salts of hydrochloric acid. 

(8) The calcium salt of sulphurous acid. 

(9) The two iron salts of sulphuric acid. 

(10) The two mercury salts of hydrochloric acid. 

4. Write the formulas of the salts of Exercise 3. 

5. Write the names of the compounds represented by the 
following formulas : 

(1) H 2 S0 4 (2) HC1 (3) HN0 3 (4) HC 2 H 3 2 

(5) CaS0 4 (6) Fe 2 (S0 4 ) 3 (7) Ag 2 S0 4 (8) HgN0 3 

( 9 )Hg(N0 3 ) 2 (io)AuCI, (n)FeS0 4 (12) KI 

(13) PbS (14) PbS0 4 (15) Na 2 SO^ (16) KN0 3 

(17) KN0 2 (18) Mg(N0 2 ) 2 (19) Mg(N0 3 ) 2 (20) CaC 4 H 4 5 



9 o 



ELEMENTARY HOUSEHOLD CHEMISTRY 



6. Write formulas of : 

(i) Oxalic acid 
(3) Calcium oxalate 
(5) Silver chloride 
(7) Nitric acid 
(9) Calcium nitrate 
(11) Magnesium acetate 
(13) Sulphuric acid 
(15) Ferrous sulphate 



(2) Sodium oxalate 
(4) Hydrochloric acid 
(6) Magnesium chloride 
(8) Potassium nitrate 
(10) Acetic acid 
(12) Sodium acetate 
(14) Sodium sulphate 
(16) Potassium bicarbonate 



CHAPTER XV 



ALKALIES 

Contrasted with acids in their effects upon litmus are the 
alkalies. 



Experiment 43. 






Materials : 






Salt 


Baking soda 


Lemon, slice 


Sugar 


Washing soda 


Apple, slice 


Vinegar 


Cream of tartar 


Slaked lime 


Alum 


Ammonia water 


Saltpeter 


Borax 


Epsom salt 


Ferric chloride 



Taste each of the above-named materials and note which of 
them are sour. Dissolve the solids in water. Squeeze out the 
juice of the lemon and apple. Test all the liquids thus obtained 
with red and with blue litmus paper. Record results in tabular 
form as follows : 





Taste 


Reaction to Litmus 


Sour 


Not Sour 


Acid 


Alkaline 


Neutral 


Lemon, etc. 


Salt, etc. 











Alkalies 

Some salts affect litmus in the same way as acids — turning 
blue to red. These are said to have an acid reaction. Ex- 
amples are alum, zinc sulphate, and cream of tartar. A 
considerable number have no action on either red or blue 
litmus. These are said to have a neutral reaction. Salt, 
saltpeter, and Epsom salt are neutral. Still others have an 
effect directly the opposite of that of the acids ; that is, they 
turn red litmus blue. Such are said to have an alkaline re- 

91 



92 ELEMENTARY HOUSEHOLD CHEMISTRY 

action. Examples are baking soda (sodium bicarbonate), 
washing soda (sodium carbonate), and borax (sodium borate). 

Experiment 44. 

Materials : 

Sodium under oil, cut in pieces large enough to yield a test 
tube of gas in the experiment. (Cubes of 3 mm. or | inch 
are suitable for a 30 cc. test tube.) 
Lead foil (tea lead) or oiled paper in pieces f inch square. 
Caustic soda sticks f inch long. 
Red litmus paper. 
Apparatus : 
Forceps. 
Dish. 
Handle the sodium with forceps, being careful not to allow it 
to touch the hands or clothing. Examine a freshly cut surface 
of sodium and compare it with the lead and aluminium. To what 
class do all three of these substances belong? Lay the sodium on 
filter paper for a few seconds to free it from oil, then wrap it in 
the lead foil (or oiled paper) leaving a small opening at one end. 
Fill a test tube with water, cover it with the thumb, and invert 
it in a dish of water. Seizing the wrapped piece of sodium, open 
end up, with the forceps, bring it quickly underneath the mouth 
of the inverted test tube. As the water enters the wrapping and 
comes in contact with the sodium, gas is evolved and collects in 
the test tube, displacing the water. When the action ceases, 
again cover the mouth of the test tube and invert the tube. Re- 
move the thumb and immediately apply a lighted match or splint 
to the mouth of the test tube. What gas do you infer to have 
been formed by the reaction of the sodium and water ? 

Examine the liquid left in the dish, comparing it with the water 
originally used. Note its feel and its effect on red litmus paper. 

Dissolve the piece of caustic soda in half a test tube of water. 
Compare this solution with the liquid in the dish. 

To determine what elements caustic soda contains, answer the 
following questions and make Experiment 45. 

Can the gas collected in the present experiment have been 
produced by decomposition of the sodium? Why? Where 
must the sodium be at the end of the experiment? What are 
the elements of water? Which of these two elements must be a 
constituent of the caustic soda ? What two elements does caustic 




Joseph Black. — 1728-1799. 

A Scottish chemist and physicist, noted for his researches upon heat 
and for his discovery of carbon dioxide, which he called " fixed air." 
Black explained the difference between the mild and the caustic alkalies, 
the relation of lime to limestone, and the distinction between lime and 
magnesia. 



ALKALIES 93 

soda therefore contain ? Is it possible it may also contain a third 
element? If so, what? 

Experiment 45. 

Materials : 

Solutions prepared in Experiment 44. 

Aluminium foil ^ inch X f inch, two or three pieces. 

(a) Put a piece of aluminium foil in a test tube of hot water. 

(b) Heat the liquid left in the dish in Experiment 44, and put 
in a piece of aluminium foil. What difference do you observe 
in the behavior of this liquid and water ? 

(c) Heat the strong solution of caustic soda prepared in Experi- 
ment 44, drop in aluminium foil, and cover the mouth of the test 
tube loosely with the thumb for a few moments to allow the evolved 
gas to collect. Test this gas with a flame, immediately after re- 
moving the thumb. 

What gas is produced by the action of aluminium on caustic 
soda? Does aluminium act on water under the conditions of 
these experiments. (See (a).) What element must caustic soda, 
therefore, contain? Name the elements of caustic soda dis- 
covered in this experiment and the preceding one. 

The experiments just performed have illustrated the fact 
that in addition to the alkaline salts there are some other 
substances which have an alkaline reaction. These are the 
hydroxides (compounds with oxygen and hydrogen) of the 
most active metals — sodium hydroxide (caustic soda), 
potassium hydroxide (caustic potash), and calcium hydroxide 
(slaked lime, the aqueous solution of which is limewater). 

These hydroxides are designated the strong or caustic 
alkalies in contradistinction to the salts of alkaline reaction, 
which are called weak or mild alkalies — the former being 
more vigorous than the latter in such actions as characterize 
alkalies in general ; for example, in their effects upon fats, 
of which we shall learn more later. 

Experiment 46. 

Test solutions of potassium hydroxide and calcium hydroxide 
with red litmus paper. Give the common names of these two 
substances. 



CHAPTER XVI 
BASES AND BASIC OXIDES 

The hydroxides of metals are called bases. The strong 
alkalies are therefore bases. These are rather exceptional 
among bases in being soluble in water. The majority of the 
bases are insoluble ; for example, ferric hydroxide, cupric 
hydroxide, aluminium hydroxide. 

The insoluble base of a given metal (e.g. aluminium) 
can be obtained as a precipitate by adding one of the solu- 
ble bases (sodium hydroxide or potassium hydroxide) to the 
solution of a salt of the metal (such as aluminium chloride 
or sulphate). 

■ Salt of Metal A + Base of = Base of Metal A + Salt of Metal B 
Metal B 

Aluminium chlo- + Sodium = Aluminium + Sodium chloride 

ride hydroxide hydroxide (left in solution) 

(white precipitate) 
AICI3 + 3 NaOH = Al(OH) 3 + 3 NaCl 

Copper sulphate + Potassium = Copper hydroxide + Potassium sul- 
hydroxide (blue precipitate) phate 

(dissolved) 
CuS0 4 + 2KOH = Cu(OH) 2 + K 2 S0 4 

Ferric nitrate + Calcium = Ferric hydroxide + Calcium nitrate 

hydroxide (red precipitate) (dissolved) 

2 Fe(N0 3 ) 3 + 3 Ca(OH) 2 = 2 Fe(OH) 3 + 3 Ca(N0 3 ) 2 

Experiment 47. 

Materials : 

Small portions of the following solids : 
Aluminium nitrate. 
Aluminium sulphate. 
Copper sulphate. 
Ferric nitrate. 
Ferric chloride. 

94 



BASES AND BASIC OXIDES 95 

Dissolve the salts in water in separate test tubes, labeling the 
tubes. Test a portion of each solution with potassium hydroxide 
solution and another portion of each with sodium hydroxide. 
Compare the precipitates obtained where the two soluble bases 
are added to the same salt. Also compare the precipitates ob- 
tained on adding the one soluble base to two salts of the same 
metal. Save the precipitates for use in Experiment 48. 

Experiment 48. 

Treat a very small portion of one or two of the solutions with 
calcium hydroxide solution, using a much larger quantity of this 
solution than of the sodium or potassium hydroxide. 

EXERCISE 

1. Write verbal equations for the reactions involved in Experi- 
ments 47 and 48, underscoring the names of the precipitates. 

2. Rewrite the above equations in symbols, underscoring the 
formulas of the precipitates. 

Basic Oxides 

Most of the bases on drying or heating are decomposed 
into basic oxides and water. Thus : 



Base 


= Basic oxide 


+ Water 


Cupric hydroxide 


= Cupric oxide 


+ Water 


(blue) 


(black) 




Ferric hydroxide 


= Ferric oxide 


+ Water 


Magnesium hydroxide 


= Magnesium oxide 


+ Water 


Calcium hydroxide 


= Calcium oxide 


+ Water 


(slaked lime) 


(quicklime) 





With cupric hydroxide this decomposition occurs even 
in the presence of water, as is evident from the change of 
color which occurs when the blue precipitate is heated. 

Experiment 49. 

Materials : 

Copper sulphate solution. 

Specimen of cupric oxide. 
To copper sulphate solution in a test tube add sodium hydroxide 



96 ELEMENTARY HOUSEHOLD CHEMISTRY 

solution. Note the color of the precipitate. What substance is 
it? Heat to boiling. What change occurs? When this sub- 
stance is dried, it is found to be identical with that obtained by 
burning copper in oxygen, viz: cupric oxide, CuO. Compare 
the color of the heated precipitate with that of a specimen of 
cupric oxide. 

The hydroxides of most metals, however, do not show such a 
color change when they are converted into oxides by the removal 
of water from their molecules. 

In a few instances the basic oxide in the cold readily recom- 
bines with water to form the base. A striking instance is 
that of calcium oxide (quicklime) which takes up water with 
evolution of great heat in the familiar process of lime slaking 
(or slacking). 

The reaction : 

Calcium hydroxide = Calcium oxide + Water 
Ca(OH) 2 = CaO + H 2 

is thus seen to be a reversible one, running in one direction at 
high, but in the opposite direction at lower, temperature. 

Experiment 50. 

Materials : 
Quicklime. 
Red litmus paper. 
Place a small lump of good quicklime (say 10 grams) in a porce- 
lain dish and add as much warm water as the lime will absorb. 
Allow to stand for a few minutes. What change occurs in the 
lime? Treat a little of the slaked lime with water in a test tube 
and test the water with red litmus paper. 

Experiment 51. 

Materials : 

Magnesium ribbon, \ inch. 
Red litmus paper. 
Burn a piece of magnesium ribbon. What is the product? 
Place this product in a dish, add water, and stir for some time. 
Test the liquid with red litmus paper. Account for the result. 



BASES AND BASIC OXIDES 97 

EXERCISE 

1. Write equations for the reactions of Experiments 49, 50, and 

2. Write equations representing the dehydration of, that is, 
removal of water from : 

(1) Cupric hydroxide (2) Ferric hydroxide 

(3) Ferrous hydroxide (4) Magnesium hydroxide 

(5) Calcium hydroxide (6) Aluminium hydroxide 



H 



CHAPTER XVII 

REACTIONS OF ACIDS WITH BASES AND WITH 
BASIC OXIDES. IONIZATION 

Experiment 52. 

Put into a clean evaporating dish about 10 cc. (^ test tube) 
sodium hydroxide solution and a piece of litmus paper. Slowly 
add dilute hydrochloric acid, stirring constantly, until the color 
of the paper is permanently changed. Now add a few drops more 
of the sodium hydroxide solution, then a few more of the hydro- 
chloric acid solution, noting the effect on the color of the paper. 

Leaving the mixture finally just acid, take out the paper, place 
the dish on a wire gauze over a burner, and evaporate to 
dryness. Taste the product. What is it? Write an equation 
for the reaction involved in this experiment. 

Experiment 53. 

In test tubes place small portions of solutions of (a) sodium 
hydroxide, (b) potassium hydroxide, (c) calcium hydroxide. Add 
litmus solution or litmus paper and treat portions of each solution 
with (1) dilute hydrochloric acid, (2) dilute nitric acid, (3) dilute 
sulphuric acid. Note the effect on the litmus. What is the effect 
of adding more of the base ? Write equations for the reactions of 
this experiment. 

In the above experiments the acid and base are said to 
neutralize each other. In every case a salt is formed and also 
water. The formation of water is not evident because the 
reaction takes place in presence of much water. The for- 
mation of the salt could be demonstrated in each instance 
by driving off the water by evaporation, as was done in 
Experiment 52. 

The action of acids on insoluble bases is illustrated in the 
following experiments. 

98 







^ftitf 



Svante August Aurhenius. — 1859-. 

The Swedish scientist who in 1887 originated the modern theory of ionization 

of electrolytes. 



REACTIONS OF ACIDS WITH BASES 



99 



Experiment 54. 

Prepare the hydroxides of magnesium, copper, and iron (ferric 
hydroxide) as in Experiment 47. Treat one of these precipitated 
hydroxides with dilute hydrochloric acid, another with dilute 
nitric acid, and the third with dilute sulphuric acid, shaking each 
test tube well and allowing time for the reaction to complete itself. 
How are the insoluble bases affected by acids ? What compounds 
are in solution at the end of the experiments? Write equations 
for the reactions of the acids on the bases. 

Bases, both soluble and insoluble, then, readily react 
with acids, yielding salts and water. Thus : 

Base + Acid = Salt 



Sodium hydrox- 
ide 
(caustic soda) 
Potassium hydrox- + Nitric acid 
ide 
(caustic potash) 
Cupric hydroxide 



+ Hydrochloric = Sodium chloride 
acid (common salt) 



= Potassium nitrate 
(saltpeter) 



+ Water 

+ Water 

+ Water 



Ferric hydroxide 
Magnesium hy- 
droxide 



+ Sulphuric acid = Copper sulphate + Water 

(bluestone) 

+ Oxalic acid = Ferric oxalate + Water 

+ Sulphuric acid = Magnesium sulphate + Water 

(Epsom salt) 



If, as in the last three of the above examples, the base is 
insoluble but the salt soluble, the effect of the acid is to 
dissolve the base (by converting it into salt). 

Experiment 55. 

Materials : 
Quicklime. 

Cupric oxide, powder. 
Magnesium oxide (magnesia). 
Place small portions (J gram or less) of the above solids in test 
tubes. To the quicklime add dilute hydrochloric acid, to the 
cupric oxide dilute nitric acid, and to the magnesia dilute sulphuric 
acid. Warm gently. 

Experiment 56. 

Make cupric oxide by adding sodium hydroxide to boiling copper 
sulphate solution as in Experiment 49. Acidify with dilute 
sulphuric acid, and warm. 



IOO ELEMENTARY HOUSEHOLD CHEMISTRY 

We see from these experiments that basic oxides, 
whether made from the hydroxides by heating or from the 
metals by direct combination with oxygen, react with acids, 
yielding salts and water. Thus : 



Basic oxide 


+ Acid 


Salt 


+ Water 


Calcium oxide 


-f Hydrochloric 
acid 


= Calcium chloride 


+ Water 


Cupric oxide 


+ Sulphuric acid 


= Copper sulphate 


+ Water 


Ferric oxide 


+ Oxalic acid 


= Ferric oxalate 


+ Water 


Magnesium oxide + Sulphuric acid 


= Magnesium sul- 


+ Water 






phate 





Whenever the salt formed is soluble in water, the acid 
dissolves the oxide. This, however, is not simple solution 
like that of salt or sugar in water. It is solution on account 
of chemical action producing a soluble product. 

EXERCISE 

Rewrite the above equations, using symbols. 

Ionization 

Solutions of acids, bases, and salts in water have a number 
of characteristics distinguishing them from other solutions, 
whether those others be aqueous solutions of substances of 
other classes (such as sugar, alcohol, glycerin, or hydrogen 
peroxide), or whether they be solutions in other solvents 
than water. 

i. Water is practically a non-conductor of electricity. 
Solutions of so-called " indifferent " substances (alcohol, 
sugar, hydrogen peroxide, etc.) are also non-conductors. 
But aqueous solutions of acids, bases, and salts conduct 
the electric current. In acting as conductors these sub- 
stances do not remain unchanged as do metallic conductors 
such as copper wire. On the contrary, they undergo con- 
tinuous decomposition as the current passes. For this reason 



IONIZATION IOI 

they are called electrolytic conductors or more briefly elec- 
trolytes (from a Greek verb, luo, I loose). When an electric 
current is passed through a solution of hydrochloric acid, 
for example, chlorine is set free at one electrode and hydrogen 
at the other. Again, when the current is passed through 
sodium chloride solution, chlorine is set free at the same 
electrode as in the case of hydrochloric acid; at the other 
electrode sodium is, no doubt, set free, but it immediately 
reacts with the water, producing hydrogen and sodium hydrox- 
ide. What we observe at the latter electrode, therefore, is 
that hydrogen gas is given off and that the water becomes 
alkaline, due to the production of sodium hydroxide. When 
a current is passed through an aqueous solution of sulphuric 
acid, the products obtained are hydrogen at one electrode, 
oxygen at the other. (See Expt. 16, p. 12.) This is quite 
consistent with the supposition that the primary products 
are hydrogen and the sulphuric acid (or sulphate) radicle 
= SO4, and that the latter, being incapable of independent 
existence, reacts with water: 

= S0 4 + H 2 = H2SO4 + O 

Thus, oxygen is liberated and the sulphuric acid is regen- 
erated. The net result is, therefore, the decomposition of 
water, and we ordinarily speak of the process as the " elec- 
trolysis of water." 

The passage of a current through sodium hydroxide solu- 
tion likewise yields hydrogen and oxygen as final products. 
The primary products are (a) sodium, which reacts with 
water, liberating hydrogen and regenerating the sodium 
hydroxide : 

Na + H 2 = NaOH + H 

(b) the hydroxyl radicle, — OH, which is immediately con- 
verted into water and oxygen : 

2 —OH = H 2 + O 



102 ELEMENTARY HOUSEHOLD CHEMISTRY 

2. Reactions between dissolved acids and bases (neutral- 
ization) are instantaneous. So, also, are reactions between 
two salts (precipitation reactions), e.g.: 

Silver nitrate + Sodium chloride = Silver chloride -f- Sodium nitrate 
Reactions between non-electrolytes in solution are usually 
much slower. 

3. All the electrolyte chlorides give the same precipitate 
(silver chloride) with all silver salts. All sulphates (in- 
cluding sulphuric acid) give the same precipitate (barium 
sulphate) with all barium salts. 

Experiment 57. 

Materials : 

Solutions of sodium chloride, potassium chloride, magnesium 

chloride, calcium chloride, aluminium chloride. 
Solutions of silver nitrate and silver sulphate. 
Solutions of sodium sulphate, potassium sulphate, magnesium 

sulphate. 
Solutions of barium chloride, barium nitrate, and barium 
acetate. 
Mix a little of each chloride solution with a little of each silver 
solution (10 experiments in all) and compare the precipitates 
produced. Also mix dilute hydrochloric acid with a little of each 
of the silver solutions. 

Mix a little of each sulphate solution with a little of each barium 
solution (9 experiments) and compare the precipitates. Also mix 
dilute sulphuric acid with a little of each of the barium solutions. 

These and other peculiarities of electrolyte solutions are 
explained by assuming that when an electrolyte dissolves 
in water, some of its molecules immediately undergo a revers- 
ible decomposition into what are called ions. 

The mode of ionization of a few acids, bases, and salts is 
illustrated by the following equations: 

Hydrochloric acid : HC1 ^H+ + Cl~ 

Sulphuric acid : H 2 S0 4 ^± 2 H+ + S0 4 " 

Acetic acid : HC 2 H 3 2 ^ H+ + C 2 H 3 2 - 

Tartaric acid : H 2 C 4 H 4 6 ^£ 2 H+ + C 4 H 4 6 — 

Citric acid : H 3 C 6 H 5 7 ^ 3 H + + C 6 H 5 (V " " 



IONIZATION 103 



Ionization of bases 



Sodium hydroxide : NaOH ^±Na + + OH - 
Calcium hydroxide : Ca(OH) 2 ^±Ca ++ + 2 OH" 

Ionization of salts : 

Sodium chloride : NaCl ^ Na+ + Cl~ 

Sodium sulphate : Na 2 S0 4 Zjl 2 Na + + S04~ ~ 

Sodium bisulphate : NaHS0 4 ^t Na+ + H++ S0 4 ~ 

Magnesium chloride : MgCl 2 ^ Mg ++ + 2 Cl _ 

Magnesium sulphate: MgS0 4 Z^^g ++ + S0 4 ~~ 

Aluminium nitrate : A1(N0 3 ) 3 ;± Al +++ + 3 N0 3 ~ 

The double arrows, used in place of the usual equality 
sign, signify that the reaction is a reversible one. There 
are always present in the solution some un-ionized molecules 
of the acid, base, or salt. In some instances, e.g. acetic 
acid, most of the molecules are un-ionized; in others, e.g. 
sodium chloride, there are only a few un-ionized molecules. 
When a solution is diluted (by adding more water), more of 
the molecules ionize. When the solution is concentrated 
(by evaporating off some of the water), some of the ions 
recombine into molecules ; when it is evaporated to dryness, 
all of the ions recombine into molecules. 

All acids yield the hydrogen ion, H + , as their positive ion 
(cation). The effects of acids on litmus may, therefore, be 
regarded as an action of the hydrogen ion. When an acid 
acts on a metal, the hydrogen ions are converted into mole- 
cules of hydrogen gas and the molecules of metal are con- 
verted into metal ions. 

All bases yield the hydroxyl ion, — OH, as their negative ion 
(anion). The action of bases on litmus or other indicators 
is, accordingly, a reaction of the hydroxyl ion. The neutral- 
ization of an acid by a base involves the combining of the 
hydrogen ions with the hydroxyl ions to form water mole- 
cules. Thus, when hydrochloric acid and sodium hydroxide 



104 ELEMENTARY HOUSEHOLD CHEMISTRY 

solutions are mixed, the hydrogen and hydroxyl ions dis- 
appear, but the sodium and chloride ions remain : 

Na + + OH" + H + + CI" = Na + + CI" + H 2 

When the insoluble base magnesium hydroxide, Mg(OH) 2 
is acted upon by hydrochloric acid, the magnesium is con- 
verted into ions : 

Mg(OH) 2 + 2 H + + 2 cr = Mg ++ + 2 cr + 2 H 2 



CHAPTER XVIII 

METAL TARNISHES 

Most metals, when heated in oxygen or air, readily com- 
bine with the oxygen. The following are examples of oxides 
formed from metals in this way : 

Magnesium oxide or magnesia, MgO. (See Expt. 51, p. 96.) 

Calcium oxide or quicklime, CaO. 

Aluminium oxide or alumina, A1 2 3 . 

Cupric oxide (black), CuO. 

Magnetic iron oxide (black), Fe30 4 . 

Sodium peroxide, Na 2 C>2. 

In the presence of moisture such combination of metal 
with oxygen occurs also at ordinary temperatures, though at 
a much slower rate than when the metal is heated. In case 
the oxide formed upon the surface adheres closely to the 
metal, the oxidation soon comes to a stop, because the film 
of oxide prevents the air coming in contact with any more of 
the metal. Magnesium, zinc, and aluminium form light- 
colored tarnishes of this kind, and consequently retain their 
whitish color, although losing something of their metallic 
luster. Lead also tarnishes rapidly by oxidation, but the 
oxide formed is darker in color than the metal itself. 

Experiment 58. 

Materials : 

Magnesium ribbon. 
Zinc sheet or rod. 
Aluminium. 
Lead. 

Emery cloth. 
Polish a little of each of the metals and compare the freshly 
polished with the tarnished surface. 

105 



106 ELEMENTARY HOUSEHOLD CHEMISTRY 

Platinum, gold, and tin do not tarnish. Nickel tarnishes 
very slowly, the tarnish being yellowish. 

Silver is not acted upon by oxygen, or by any other con- 
stituent of pure air, but takes a black tarnish of silver sulphide, 
Ag 2 S, when exposed to the action of the element sulphur. 
It is also tarnished in the same way by many compounds of 
sulphur. Small quantities of sulphur compounds are some- 
times present in the air, particularly where coal is burnt or 
coal gas used and in the neighborhood of smelting works. 

Silver is also tarnished by contact with organic materials 
containing sulphur ; for example, vulcanized rubber and the 
proteins of foods (such as eggs) and of wool. Silverware 
should not be wrapped in any fabric containing wool nor in 
bleached or dyed cotton goods in the manufacture of which 
sulphur may have been used. Soft unbleached cotton goods 
and tissue paper make suitable wrappings for silver. 

In the tarnishing of copper the carbon dioxide present 
in the air plays a part as well as the oxygen and moisture. 
The product is a carbonate of copper. This is soluble in 
dilute acids such as are present in fruits. Bright copper is 
not acted upon by such acids. A bright copper kettle may 
therefore be safely used in preserving or other cooking opera- 
tions, but not a tarnished one. Brass and bronze are alloys 
of copper, i.e. materials made by combining copper with 
other metals — zinc for brass, tin (sometimes together with 
other metals) for bronze. The tarnish of brass and bronze 
is similar to that of copper. 

Removal of Tarnish 

The basic oxides which constitute the tarnish of most 
metals are, of course, soluble in suitable acids. But the use 
of acids for the removal of tarnish from metals is seldom 
resorted to. In some instances it would be difficult to find 
a suitable acid — one that would dissolve the oxide without 



METAL TARNISHES 107 

attacking the metal. It has also to be remembered that 
there is usually other dirt to be removed in addition to 
the tarnish compound and also that the surface of the 
metal, which has been roughened by the formation of the 
oxide, must be polished smooth in order that it may appear 
bright. 

The polishing of metals is usually done with a cloth or 
piece of soft leather, such as chamois, and a fine powder as 
whiting, rottenstone, or rouge. When polished metals are 
examined under the microscope, they are found to be covered 
with a thin film, in which the metal behaves more like a 
liquid than a solid. The smooth, level film reflects light just 
as the surface of mercury does. This film is produced by the 
pressure of the cloth and polishing powder, both of which are 
softer than the solid metal. The presence of hard particles 
in the polishing powder, and especially that of large hard 
particles, is to be avoided. Suitable materials for polishing 
copper, brass, bronze and nickel are rouge, Venetian red, 
whiting, putty powder, and rottenstone (called also tripoli). 
For silver and aluminium, which are softer metals, whiting, 
rouge, or putty powder should be used. 

The polishing powder may advantageously be mixed into 
a paste with an oil or grease, or it may be made up in paste 
or semi-liquid form with a suitable liquid — either one that 
will dissolve grease or one that will dissolve the tarnish 
compound. Ammonia, which dissolves the oxides of copper 
and nickel, may be used in polishes for these metals and 
for brass and bronze. \ Acids, such as oxalic, citric, cream of 
tartar, lemon juice, buttermilk, and vinegar (or vinegar and 
salt) are sometimes recommended for silver, copper, and 
brass. Their efficacy doubtless depends upon their action 
on the oxide films. When any of these tarnish solvents, 
or polishes containing them, are used, care must be taken 
to leave none of the active agents on the metal, for the 
reason that they would promote the oxidation of the metal. 



108 ELEMENTARY HOUSEHOLD CHEMISTRY 

Experiment 59. 

Material : 

Copper oxide, powder. ^ 

Shake a very little powdered copper oxide with ammonia in a 
test tube. Allow to settle and note the color of the liquid. 

Experiment 60. 

Materials : 
Copper foil. 
Whiting. 

Moisten a little whiting with a few drops of ammonia. Dip a 
rag in this paste and polish both sides of the copper foil. Cut the 
foil into three pieces. Wash two of these thoroughly. Place one 
of the washed pieces in a test tube, partly cover with ammonia 
water, and leave standing for a few minutes, shaking occasionally. 

Leave the unwashed piece of foil standing for a few hours. 
Then compare it with the washed piece. Explain the results. 

Among the liquids used in metal polishes on account of 
their action upon grease are alkalies, such as aqueous solu- 
tions of soda, ammonia, ammonium carbonate, borax, and 
soap ; and hydrocarbons, such as kerosene (coal oil), gasoline, 
benzine, and turpentine. Sometimes both a hydrocarbon 
and an alkali is used, e.g. soft soap and turpentine. 1 A 
mixture of whiting with alcohol and a few drops of ammonia 
makes a good polish for aluminium as well as for silver. 

Brass may be prevented from tarnishing by covering with 
a lacquer which prevents the air coming in contact with the 
metal. Lacquers are solutions of shellac in alcohol (1 to 4 
ounces shellac to 1 pint of alcohol). To the simple lacquer 
various red and yellow coloring matters are added. The 
metal to be lacquered is scrupulously cleaned, and the lac- 
quer is very evenly applied with a camePs-hair brush or by 
dipping, and is allowed to dry without being touched. 

1 Many recipes for polishing powders may be found in such books as "The 
Scientific American Cyclopedia of Receipts, Notes, and Queries " or Seaman's 
" Expert Cleaner." 



CHAPTER XIX 

IRON RUST 

Iron is at the present day the most useful of all the metals. 
So large a part does it play in modern life that ours has been 
called the " Iron Age." By modifying the processes by which 
iron ores (which are chiefly oxides of iron) are converted into 
the commercial forms of the metal we obtain products dif- 
fering considerably in strength and hardness and therefore 
suitable for different uses. We have, for instance, the soft, 
tough wrought iron and mild steel used in wire, horseshoes, 
andirons, and all other products shaped on the anvil ; the 
hard steel, capable of being tempered to various degrees of 
hardness and elasticity for use in razors, penknives, scissors, 
tableknives, and watch springs, and the brittle cast iron, 
more easily melted than the other kinds of iron and used 
in making objects that have to be molded to a definite 
shape, for example, the frames and treadles of sewing 
machines. 

As compared with most of the common metals, iron has 
one serious defect, the consequences of which have always 
to be carefully guarded against. It tarnishes readily, and the 
tarnish, called rust, does not adhere closely to the surface 
of the metal, as do the tarnishes of magnesium, aluminium, 
zinc, and copper. Iron rust scales off and thus continually 
exposes new surface of metal to the corroding effect of the 
air. The prevention of the corrosion of iron and steel goods 
is, therefore, an important economic problem. 

Iron rust is a red, powdery substance, consisting of ferric 

109 



HO ELEMENTARY HOUSEHOLD CHEMISTRY 

oxide, Fe 2 03, or, strictly speaking, of a substance inter- 
mediate in composition between ferric oxide and ferric hy- 
droxide, Fe(OH)3. It is therefore a substance similar to the 
oxides and hydroxides of other metals. 

There are two general methods of preventing rusting of 
iron. One is to keep the metal dry and brightly polished. A 
rust-free surface rusts much less readily than one already 
spotted, and a polished surface is less liable to rust than a 
rough one. Water and carbon dioxide promote rust forma- 
tion. Indeed, rust cannot form in absence of water. If, 
therefore, the iron is brightly polished and kept dry, it will 
not corrode. This is the method commonly used to keep 
household cutlery bright. The more promptly knives and 
forks are scoured and dried after use, the less labor will be 
involved in keeping them in prime condition. 

The second method of preventing rusting is to cover the 
iron with some material which will protect it from the air. 
A great variety of coverings are used for different purposes. 
A covering of oil or of vaseline is sufficient for some purposes, 
e.g. for tools, knives, etc., which are to be laid away for some 
time. Melted paraffin wax may be used for the same pur- 
pose as well as for smoothing irons before they are put away 
on ironing day. 

Stoves and stovepipes which are to be temporarily stored 
may also be oiled. But it is perhaps better to varnish them 
with a thin solution of asphalt in turpentine, which will 
burn off when they are put into use again. Common stove 
polish is made of graphite, a mineral form of the element 
carbon, which burns very slowly, and without odor. Other 
names for graphite are plumbago and black lead. 1 

1 The word "graphite" is derived from the Greek grapho, I write, and the 
word "plumbago" from the Latin, plumbum, lead. All three names — graphite, 
plumbago, and black lead — are derived from the circumstance that this form 
of carbon is so soft that, like lead, it will mark on paper. "Lead " pencils are 
made of a mixture of graphite with clay. 



IRON RUST III 

More permanent coatings for iron are paint, japan, enamel, 
and less corrodible metals. Paint is used on the structural 
steel of bridges, as well as on wagons, agricultural machinery, 
and other outdoor hardware ; also on water-pipes and some 
other indoor articles. Carriage hardware, tea trays, the 
handles of scissors, and many other small articles are 
japanned, i.e. covered with a lacquer, which is then baked 
on, polished, and varnished. 

Enamelware is now very commonly used in the kitchen. 
This is iron covered with a glaze similar to that used on 
porcelain and chinaware. It is put on in a molten condi- 
tion, and solidifies on cooling. Enamelware is particularly 
satisfactory for culinary vessels, as it resists the action of the 
acids contained in foods, as well as that of the oxygen of the 
air. In using enamelware care should be taken not to crack 
the enamel by shock or by too rapid heating or cooling of the 
dry vessel. 

Among the metals used to cover iron to protect it from the 
air are : 

(a) Zinc. Iron covered with zinc is said to be " gal- 
vanized." The word is derived from the name of Galvani, 
the discoverer of the electric current, but the modern pro- 
cesses of galvanizing iron consist simply in immersing the 
cleaned iron in molten zinc, passing the sheet between rollers, 
and allowing to cool. 

(b) Tin. Ordinary tinware is made of " tinplate," which 
is sheet iron covered with tin by a process similar to that used 
with zinc. 

(c) Nickel. Iron is sometimes nickel-plated, the nickel 
being welded to the iron. 

The magnetic oxide of iron, Fe 3 C>4, formed by the action 
of atmospheric oxygen, or by that of very hot steam, on hot 
iron, adheres closely to the iron. In this respect it differs 
from rust, but it resembles the oxides of other metals. This 
fact has been utilized to prevent rusting. The iron is heated 



112 ELEMENTARY HOUSEHOLD CHEMISTRY 

in a furnace and superheated steam is blown in upon it. Iron 
with a blue finish has been so treated. 

When once the covering layer is broken at a single point, 
tinware and nickelware will rust more rapidly than iron which 
has not received a protective coating. The same is true of 
iron covered with magnetic oxide, and probably also of 
enamel ware. Galvanized iron, however, when similarly 
injured, does not corrode as fast as unprotected iron. 
The zinc appears to exert a protective action, even upon the 
exposed parts of the iron. This is one reason why gal- 
vanized iron is preferred to tinware for outdoor use. On the 
other hand, zinc is acted upon by vegetable acids. Hence 
galvanized iron is not suitable for culinary vessels or for 
receptacles for soft fruits, milk, or any acid food. 

Rust Stains on Fabrics 

• Linen, cotton, and other textiles not infrequently become 
soiled with iron rust. Iron-rust stains are sometimes called 
" iron mold," possibly on account of some confusion with 
mildew, which is really a mold. Being composed of ferric 
oxide, which is insoluble in water and in alkalies, such stains 
are not removed by the ordinary washing processes. Like 
other basic oxides, however, iron oxide is converted into sol- 
uble salts by the action of suitable acids. 

Experiment 61. 

Materials : 
Oxalic acid. 
Acid potassium oxalate. 

Heat about 10 cc. (^ test tube) of ferric chloride solution to 
boiling and add sodium hydroxide solution. What is the precipi- 
tate ? Write equation for the reaction by which it was produced. 

Allow the precipitate to settle, pour off the supernatant liquid, 
add water, shake, allow to settle, and again pour off. (This is 
called washing by decantation.) Finally add a half test tube of 
water, shake thoroughly, and divide into five equal portions in test 



IRON RUST 113 

tubes. To these add respectively: (1) dilute hydrochloric acid, 
(2) dilute sulphuric acid, (3) acetic acid, (4) oxalic acid, dissolved 
in hot water, (5) acid potassium oxalate, dissolved in hot water. 
Which of these acids dissolve the precipitate ? Write equations for 
reactions. (In the last reaction potassium oxalate is formed as 
well as ferric oxalate.) 

The acid chosen for the removal of rust stains from tex- 
tile fabrics must be one that will do the work quickly and 
thoroughly but without injury to the textile itself. 

Those most commonly employed are oxalic acid, H2C2O4, 
and its acid potassium salt, KHC2O4. This acid salt is com- 
monly known as " salt of lemon " or " salts of lemon," al- 
though actually oxalic acid does not occur in lemons. Salt 
of sorrel is a more appropriate name. The action of this 
salt is less vigorous — both on the rust and on the fabric — 
than that of free oxalic acid. 

Any of the acids used to remove rust stains may injure 
the fabric if not thoroughly washed out. As the fabric dries, 
the acid solution becomes more and more concentrated until 
it reaches a concentration at which it acts upon the textile 
fibers and weakens them. This may occur even with the 
volatile acid, hydrochloric, which may reach the concentra- 
tion of 20 per cent hydrochloric acid before drying off com- 
pletely. Goods which have been treated with acid for the 
removal of rust stains should be washed immediately in pure 
water, and afterwards in water containing a little ammonia. 



CHAPTER XX 

STRONG AND WEAK ACIDS AND BASES 

Experiment 62.* 

Materials : 

3 equal pieces of magnesium ribbon, each weighing about 0.04 

gram. 
Lead foil, e.g. tea lead. 
3 eudiometer tubes, 50 cc. 
3 dishes, e.g. glass evaporating dishes. 
Stands and clamps. 

Normal (or approximately normal) solutions of hydrochloric, 
acetic, and formic acids. 1 
Fill one eudiometer tube with each acid solution, invert it in a 
dish of the same acid, and clamp it with the mouth a little below 
the surface of the liquid in the dish. Attach each of the pieces 
of magnesium ribbon to a piece of lead foil (e.g. by passing it through 
a slit in the latter) so that the magnesium cannot rise in the liquid. 
Bring the anchored pieces of ribbon quickly beneath the mouths 
of the eudiometers and compare the rates at which the hydrogen 
gas collects in the eudiometers. 

Experiment 63. 

Materials : 

The normal acid solutions used in Experiment 62. 
3 pieces of marble of about equal size and form. 

1 If the laboratory reagents are on the normal system, the two former can 
be made by diluting the reagent dilute hydrochloric and acetic acids. A normal 
solution of formic acid may be made from pure formic acid (specific gravity 1.22) 
by diluting 37.7 cc. to 1 liter; and from acid of specific gravity 1.06 by diluting 
173.6 cc. to 1 liter. Normal acetic acid may be made by diluting 57.1 cc. of 
glacial acetic acid to 1 liter. Normal hydrochloric acid may be made as follows : 
Dilute 105 cc. concentrated acid or 165 cc. of acid of specific gravity 1.10 to 1 
liter. Compare the solution so obtained with a normal solution of sodium 
carbonate — 53 grams of the pure, dry salt to 1 liter — by adding to the latter 
two or three drops of methyl orange solution and running in the acid from a 
burette until the well-mixed solution is just red. Then dilute the acid solution 
to such a strength that 10 cc. of it will exactly neutralize 10 cc. of the normal 
sodium carbonate solution. 

114 



STRONG AND WEAK ACIDS AND BASES 115 

Put the three pieces of marble in separate test tubes and pour 
one acid on each. Compare the rates at which gas (carbon dioxide) 
is evolved, and also the rates at which the marble is dissolved. 
Do the three acids arrange themselves in the same order with 
respect to their activity in dissolving marble as they did with 
respect to their activity in dissolving magnesium? 

Some acids are much more active than others. If we 
take two quarts of water and dissolve in one enough hydro- 
chloric acid, in the other enough acetic acid, to yield one cubic 
foot of hydrogen gas by their action on zinc or magnesium, 
the hydrochloric acid will produce the gas much more rapidly 
than the acetic, although ultimately the same quantity will 
be set free from both. Hydrochloric acid also excels acetic 
in the speed of its action upon metallic oxides (such as mag- 
nesia, cupric oxide, etc.) and upon marble. 

Compared in these and many other ways, hydrochloric 
acid is always found to be more active than acetic. For this 
reason it is designated a strong acid, whereas acetic acid is 
classed as weak. The relative strengths of other acids may 
be similarly compared, and by methods not very different 
the relative strengths of bases may be compared. The results 
of such comparison lead to the following classification : 

Acids : 

Strong : Hydrochloric, Nitric, Sulphuric. 
Moderately strong : Oxalic, Tartaric, Citric. 
Weak : Acetic, Palmitic, Stearic, Oleic. 
Very weak: Carbonic, Boric (or Boracic). 

Bases : 

Strong: Sodium hydroxide (caustic soda), Potassium hy- 
droxide (caustic potash), Calcium hydroxide (slacked 
lime — in aqueous solution, lime water). 

Moderately strong : Magnesium hydroxide. 

Weak : Ammonium hydroxide. 



Il6 ELEMENTARY HOUSEHOLD CHEMISTRY 

Very weak : The hydroxides of copper, iron, aluminium, 

and most other metals. 
The student should memorize the above classification. 

Ionization Theory of the Strength of Acids and Bases 

According to the theory of ionization, as we have seen 
(p. 103), the characteristics common to all acids in aqueous 
solution are due to the hydrogen ion contained in all these 
solutions. Accordingly, the more ionized hydrogen there 
is in a given volume of water the more marked will these 
characteristics be. The " normal " solutions of hydrochloric, 
formic, and acetic acid used in Experiments 62 and 63 con- 
tain equal quantities of ionizable hydrogen in a given volume, 
viz. 1 gram per liter. But the hydrochloric acid solution had 
more of this hydrogen actually ionized than either of the 
others. This is evidenced not only by the greater activity 
of the hydrochloric acid, but also by the fact that a normal 
solution of hydrochloric acid is a very much better conductor 
of electricity than a normal solution of formic or of acetic 
acid. It is the ions which, traveling through the solution, 
conduct the electric current. The un-ionized molecules 
play no part in conduction. The superior conducting power 
of the hydrochloric acid solution is largely due to the great 
proportion of ionized molecules present in its solution as 
compared with those in normal solutions of the formic and 
acetic acids. It is estimated that in a normal solution of 
hydrochloric acid 780 out of every thousand molecules are 
ionized, while in formic acid only 14 and in acetic acid only 
4 in a thousand are ionized. 

Strong acids are, therefore, highly ionized acids, weak acids 
slightly ionized acids. Similarly, strong bases are highly 
ionized and weak bases only slightly ionized, and the superior 
activity of the strong bases is due to the greater quantity of 
hydroxyl ions, OH - , present in a given volume of solution. 



CHAPTER XXI 

HYDROLYSIS OF SALTS 

Experiment 64. 

Materials : 

Litmus paper, red and blue. 
Distilled water. 

Small quantities of the following salts : Sodium chloride 
(salt) ; sodium sulphate (Glauber's salt) ; potassium nitrate 
(saltpeter) ; sodium carbonate (washing soda) ; sodium 
borate (borax) ; ammonium carbonate (smelling salt) ; 
ferric chloride (perchloride of iron) ; ferrous sulphate (cop- 
peras) ; aluminium sulphate ; soap (contains sodium pal- 
mitate, sodium stearate, and sodium oleate) ; copper sul- 
phate (blue stone) ; sodium bicarbonate (baking soda). 
In distilled water in clean test tubes dissolve the salts named 
above, and test the solutions with red and with blue litmus paper. 
Tabulate, as illustrated below, the salts, their reactions to litmus, 
the acids and bases to which they correspond, and the relative 
strengths of these latter : 



Salt 


Acid 


Base 


Name 


Reaction 


Name 


Strength 


Name 


Strength 


Stannous 
chloride 


Acid 


Hydro- 
chloric 


Strong 


Stannous 
hydroxide 


Weak 



Look over your results and state what general relations there 
are between the reactions of salts and the relative strengths of the 
acids and bases to which they correspond. 

When the salt of a weak acid or the salt of a weak base 
is dissolved in water, the water acts upon the salt, partially 
reversing the action by which the salt and water are formed 

117 



Il8 ELEMENTARY HOUSEHOLD CHEMISTRY 

from acid and base. That is to say, the following reaction 
takes place upon a part of the dissolved salt : 

Salt + Water =; ^Acid + Base 

This, it will be noticed, is the reverse of the reaction of 
acid with base which we studied in Chapter XVII. 

Whenever a compound is acted upon by water with the 
production of two new compounds, it is said to be hydrolyzed 
(literally, split up by Jie action of water). Thus, in the above 
reaction, the salt is said to undergo hydrolysis. 

Now, if the salt is one of a weak base with a weak acid (e.g. 
aluminium carbonate), it may be completely decomposed by 
the action of water. 

Experiment 65. 

To ferric chloride solution add sodium carbonate solution. 
Note the immediate formation of a precipitate, and watch for sub- 
sequent action. Test the gas evolved with a film of limewater 
in the glass loop. (See Expt. 5, p. 5.) 

Carbonic acid, when it is formed, soon breaks up into water 
and carbon dioxide : 

H2CO3 = H 2 + C0 2 

If the precipitate is examined after this action ceases, it is found 
to be the base, ferric hydroxide, Fe(OH) 3 . 

Make the same experiment with aluminium sulphate instead of 
ferric chloride. The white precipitate remaining in the test tube 
after the action ceases is the base, aluminium hydroxide. Write 
equations representing the hydrolysis of: (a) ferric carbonate, 
(b) aluminium carbonate. 

If the salt treated with water is one of a weak base with a 
strong acid, it is not completely, but only partially, hydrolyzed, 
but the water acquires an acid reaction from the strong acid 
produced. Examples are aluminium sulphate, ferric chloride, 
and copper nitrate. Solutions of these salts turn blue litmus 
red. 

If the salt corresponds to a strong base and a weak acid, 



HYDROLYSIS OF SALTS 119 

it is partially hydrolyzed and imparts an alkaline reaction 
to the water. Examples are sodium carbonate (washing 
soda) and sodium borate (borax). Solutions of these turn 
red litmus blue. These are the mild alkalies previously 
referred to (p. 93). 

Salts of strong acids with strong bases are not hydrolyzed. 
Their solutions are quite neutral, like water itself. Examples 
are sodium chloride (common salt), sodium sulphate (Glau- 
ber's salt), and potassium nitrate (saltpeter). 

The effect of water on the salt of a weak base and a strong 
acid is well illustrated in the following experiments with 
a substance much used in the household, viz. soap. Hard 
soap is a mixture of the sodium salts of the three weak acids, 
palmitic, stearic, and oleic. Soft soap is a mixture of the 
potassium salts of these same acids. 

EXERCISE 

1. Write the names of these sodium and potassium salts. 

2. Write equations for the hydrolytic reactions studied in Ex- 
periment 64. 

Experiment 66. 

Materials : 

Soap, good quality, in shavings. 
Phenolphthalein solution. 

Phenolphthalein is an indicator, i.e. a substance which, like 
litmus, has a different color in acid solution from what it has in 
alkaline solution. It is used in this experiment in preference to 
litmus because it is soluble in alcohol, whereas the active con- 
stituent of litmus is not. To discover what color the phenol- 
phthalein takes in acid, neutral, and alkaline solutions, add a drop 
or two of the solution of this indicator to (a) a little dilute acid, 
(b) a little distilled water, (c) a little dilute alkali. 

Dissolve a little of the soap in warm water and a little in alcohol. 
Add a drop or two of phenolphthalein to each solution. What 
difference is observed? Now add water to the alcoholic solution. 
What change occurs ? What do you infer as to the action of water 
on the soap salts? 



120 ELEMENTARY HOUSEHOLD CHEMISTRY 

Poorly made soap may contain some " free alkali ", i.e. 
sodium hydroxide. This can be determined by dissolving 
the soap in alcohol and adding a drop or two of phenol- 
phthalein solution. Good soap will not give a color. Soap 
containing free alkali will yield a pink color. 

Experiment 67. 

Materials : 

Samples of commercial and homemade soaps. 

Test these soaps for free alkali by dissolving them in alcohol 
in clean water-free test tubes and adding a drop or two of phenol- 
phthalein solution. 



CHAPTER XXII 
HARD WATER 

Some natural waters are called hard on account of the 
difficulty experienced in washing with them. Soap added 
to such waters causes the separation of a curdy precipitate. 

Experiment 68. 

Materials : 

A solution of soap in water. 
Hard water. 

Solutions of calcium chloride and calcium sulphate. 
To separate portions of the soap solution add (i) calcium 
chloride solution, (2) calcium sulphate solution, (3) hard water. 
Note the curdy precipitate which rises to the top of the liquid. 

The precipitate produced when soap solution is mixed 
with the hard water is identical with that produced when it 
is mixed with a solution of calcium chloride, calcium sul- 
phate, calcium nitrate, or any other calcium salt. The re- 
action by which this precipitate is formed is one between 
the calcium ion and the anions of the soap — the palmitate, 
stearate, and oleate ions. The precipitate consists of calcium 
palmitate, calcium stearate, and calcium oleate and may 
appropriately be termed calcium soap. Just as the silver 
ion, contained in solutions of silver salts, precipitates the 
chloride ion of potassium chloride, sodium chloride, etc., 
forming silver chloride (see p. 102), so the calcium ion, con- 
tained in all solutions of calcium salts, precipitates the pal- 
mitate, stearate, and oleate ions of soap solutions, forming 
the insoluble calcium soap. 

Hard water, then, is water containing the calcium ion. 1 

1 Some hard waters contain the magnesium ion, which also produces precipi- 
tates with the palmitate, stearate, and oleate ions. 

121 



122 ELEMENTARY HOUSEHOLD CHEMISTRY 

The calcium ion is present in such waters because they have 
dissolved some of the calcium salts present in the soil and 
rocks with which they have come into contact. The mineral 
called gypsum is a crystal compound of calcium sulphate with 
water. Its formula is CaS0 4 ■ 2 H 2 0. Water kept in contact 
with this mineral for a sufficiently long time will dissolve 
about -5IJ0- of its own weight of calcium sulphate. If the 
contact is less prolonged, a smaller quantity of the calcium 
sulphate will be dissolved. Another compound of very 
common occurrence as a mineral is calcium carbonate. This 
occurs well crystallized as calcite and in less pure or less 
clearly crystallized forms as marble, limestone, chalk, and 
marl. Small particles of calcium carbonate are also com- 
monly found in the soil. Pure water does not dissolve cal- 
cium carbonate appreciably. 1 But water which percolates 
through soil takes up carbon dioxide from the soil air and, 
combining with it, forms carbonic acid, which in turn combines 
with the calcium carbonate, forming a soluble compound 
called calcium bicarbonate. These reactions are represented 
by the following equations : 

C0 2 + H 2 = H 2 C0 3 

Carbon dioxide + Water = Carbonic acid 
CaCQ 3 + H 2 C0 3 = Ca(HC0 3 ) 2 

Calcium carbonate + Carbonic acid = Calcium bicarbonate 

The following experiment illustrates (1) the formation 
of the insoluble calcium carbonate from carbonic acid and 
calcium hydroxide, (2) the formation of the soluble calcium 
bicarbonate by the action of carbonic acid upon the carbonate. 

Experiment 69. 

Materials : 
Limewater. 

Carbon dioxide gas from generator or from cylinder of liquid 
carbon dioxide. 

1 It takes 100,000 parts of water to dissolve i part of calcium carbonate. 



HARD WATER 1 23 

Graduated cylinders, 25 cc. 
Soap solution. 
Dilute 25 cc. Timewater with an equal volume of distilled water. 
Pass in carbon dioxide. Note the precipitate of calcium car- 
bonate. Continue to pass in carbon dioxide for some time. What 
happens to the precipitate? 

If the solution does not become perfectly clear, filter it. Mix 
a little of this artificial hard water with soap solution. Reserve 
the remainder for Experiment 70. 

Temporary and Permanent Hardness 

Some hard waters can be softened or partially softened 
by simply boiling them. Hardness that can be thus removed 
is termed temporary hardness. Temporary hardness is due 
to calcium bicarbonate. The effect of boiling is to decom- 
pose the bicarbonate into calcium carbonate (which pre- 
cipitates), carbon dioxide, and water. Thus: 

Ca(HC0 3 ) 2 = CaCQ 3 + C0 2 + H 2 

Experiment 70. 

Measure into a test tube 5 cc. of the temporarily hard water 
obtained in Experiment 69. Add a solution of soap, little by little, 
from a burette or graduate, covering the test tube with the thumb 
and shaking vigorously after each addition. Note the quantity 
of soap solution required to give a lather which persists for one 
minute. 

Measure out a second 5 cc. of the temporarily hard water, and 
boil it for a few minutes. What separates from the liquid? Add 
soap solution from the burette or graduate as before, and note 
how the quantity of soap required differs from that required by 
the unboiled hard water. 

Hardness due to calcium sulphate cannot be removed by 
boiling. Such hardness is termed permanent hardness. 1 

Of course, the hardness of the water of a given well, lake, 
or river may be partly temporary and partly permanent. 

1 Magnesium bicarbonate also produces temporary hardness and magnesium 
chloride and sulphate permanent hardness. 



124 ELEMENTARY HOUSEHOLD CHEMISTRY 

That is to say, the same water may contain both calcium 
bicarbonate and other calcium salts, such as the sulphate. 

The Softening of Water 

The softening of water consists in the precipitation of the 
calcium (and magnesium) which it contains. Water may be 
softened by adding to it a salt having an anion which com- 
bines with the calcium ion to form an insoluble compound. 
The carbonate of calcium is insoluble. So if we add to hard 
water a soluble carbonate, the calcium will be precipitated in 
the form of its carbonate. Since washing soda is the cheapest 
soluble carbonate, it is the material most commonly used. 
If the hard water contains calcium sulphate, the reaction is : 

Calcium sul- + Sodium car- = Calcium car- + Sodium sul- 
phate bonate bonate phate 
CaS0 4 + Na 2 C0 3 = CaCQ 3 + Na 2 S0 4 

or in ionic notation : 

Ca ++ + S0 4 - + 2 Na + + CO3- = CaC0 3 + 2 Na + + SO4— 

The calcium being thus removed from solution by con- 
version into the insoluble carbonate, the water is no longer 
hard, and can therefore no longer act upon soap. In other 
words, the water now acts as a soft water. 

It is, however, not quite as satisfactory a laundry water 
as naturally soft water, because the sodium sulphate left in 
solution has a slight effect in precipitating soap. (See Expt. 
84, Chapter XXVI.) 

The action of borax (sodium borate) in softening water 
is similar to that of soda. Calcium borate is precipitated : 

Calcium sulphate + Sodium borate = Calcium borate -f- Sodium sul- 
phate 

The calcium is thus removed from the water, which there- 
after acts as a soft water. 



HARD WATER 125 

Temporarily hard water also can be softened by the use 
of soda. The reaction is : 

Calcium + Sodium = Calcium + Sodium 
bicarbonate carbonate carbonate bicarbonate 

Ca(HC0 3 ) 2 + Na 2 C0 3 = CaCQ 3 + 2 NaHC0 3 

Experiment 71. 

To 5 cc. of the temporarily hard water add sodium carbonate 
solution. Then add soap solution from a burette or graduate, 
comparing the quantity required with that used with the un- 
treated hard water in Experiment 70. 

A method sometimes used in softening municipal water 
supplies is to add lime. The reaction is : 

Calcium + Calcium = Calcium + Water 

bicarbonate hydroxide carbonate 

Ca(HC0 3 ) 2 + Ca(OH) 2 = CaCQ 3 + 2 H 2 

This method, however, is not well adapted for house- 
hold use, since it is necessary to measure the degree of hard- 
ness of the water to determine just how much lime should 
be used. 

Degrees of Hardness 

There are of course degrees of hardness of water, and the 
term is sometimes given a strict quantitative signification. 
A water is said to have one degree of hardness when it has in 
every gallon the same quantity of calcium as is contained in 
one grain of calcium carbonate ; two degrees of hardness, when 
it has twice this quantity of calcium per gallon, and so on. 

It has been estimated that each degree of hardness involves 
an increased consumption of 2 to 2§ ounces of soap for every 
100 gallons of water. This quantity of soap is used up in 
softening 100 gallons of water, and it is wasted, so far as any 
useful effect towards the washing of clothes is concerned. 
Indeed, it is worse than wasted, since the precipitate of lime 
soap forms an objectionable stain upon white fabrics. Al- 



126 ELEMENTARY HOUSEHOLD CHEMISTRY 

lowing 10 gallons of water per person per day, the soap used 
in softening hard water for a family of five would amount 
to over 21 pounds per year for each degree of hardness. Many 
hard waters have 10 to 20 degrees of hardness. It is therefore 
obvious that the waste may amount to something quite 
serious. 

A hundred gallons of hard water can be softened by the use 
of about two thirds of an ounce of washing soda crystals for 
each degree of hardness. Water for a family of five persons 
estimated as above (50 X 365 = 18,250 gallons) could be 
softened by the use of 7J pounds of soda per annum, for each 
degree of hardness. The 7! pounds of soda would cost about 
one ninth as much as the 21 pounds of soap. 

With a water of a hardness of 10 degrees the comparison 
would be between 210 pounds of soap and 75 pounds of soda. 
Adopting the wholesale prices of 6 cents per pound for soap 
and 2 cents per pound for soda, we have : 

Cost of softening with soap, 210 pounds at 6 cents . . $12.60 

Cost of softening with soda, 75 pounds at 2 cents . . 1.50 

Saving when soda is used $11.10 

In softening water with soda, the use of too much soda 
should be avoided. What is not used up in the reaction with 
the calcium compounds is left in the water. If a great excess 
is used, the water may be rendered so strongly alkaline as to 
injure delicate fabrics. 



CHAPTER XXIII 

AMMONIA AND THE AMMONIUM RADICLE 

Experiment 72. 

Materials : 

Red litmus paper. 
Turmeric paper. 
Pour a little ammonia water into a test tube. Note the odor 
and the effect produced on pieces of red litmus paper and yellow 
turmeric paper held at the mouth of the tube. Bring an open 
bottle of concentrated hydrochloric acid near the mouth of the 
test tube. What forms? 

Experiment 73. 

Materials : 

Solid specimens of : 
Ammonium carbonate. 
Ammonium chloride. 
Ammonium nitrate. 
Ammonium oxalate. 
Ammonium sulphate. 
Note whether these salts have the odor of ammonia. Is there 
an exception among them? Of the others, mix one with slaked 
lime and heat gently, heat one with sodium hydroxide solution, 
and one with potassium hydroxide solution. Note odor in each 
experiment. 

Ammonia is the name of the gas of pungent odor which 
escapes from ammonia water {aqua ammonicE, liquor am- 
monioz). Ammonia gas is formed in nature in the putre- 
factive decomposition of animal and vegetable matter con- 
taining nitrogen. The odor is often distinctly perceptible 
in horse stables in which manure has been allowed to accu- 
mulate. 

Ammonia was formerly obtained, for medicinal use, by 
destructive distillation of nitrogenous animal wastes, such 

127 



128 



ELEMENTARY HOUSEHOLD CHEMISTRY 



as bones, hoofs, and horns; hence the name, " spirit of harts- 
horn," sometimes applied to aqua ammoniae. The com- 
pound is now manufactured as-a by-product of the coal-gas 
industry. In the process of destructive distillation (heating 
the coal in closed retorts) much of the nitrogen of the coal 
escapes with the gas as ammonia, which is afterwards sepa- 
rated from the other constituents of coal gas and obtained 
pure. (See Chapter XII.) 

The gas can be converted into a liquid by cold and pres- 
sure, and in this form is used in the refrigerating machines 
of cold-storage plants and ice factories. This anhydrous 

liquid ammonia is not to be 
confounded with the more com- 
monly used liquor ammonia — 
the solution of this gas in 
water. Ammonia contains the 
elements nitrogen and hydro- 
gen and has the formula NH 3 . 

Experiment 74.* 

Materials : 

Ammonium chloride. 
Slaked lime. 
Red litmus solution. 
Apparatus: 
Figure 37. Small round- 
bottomed flask connected 
through drying tube con- 
taining quicklime to upward 
delivery tube. 
Figure 38. Fountain appara- 
tus, consisting of (a) ^-liter 
round-bottomed flask, fitted 
with tightly fitting two- 
holed stopper, carrying (1) 
a glass tube reaching nearly to bottom of flask, (2) a 
medicine dropper ; (b) a retort stand with ring to hold 
this flask in inverted position ; (c) glass dish or beaker. 




Fig. 37. — Experiment 74. Appa- 
ratus for generating ammonia. 



AMMONIA AND THE AMMONIUM RADICLE 129 



Mix ammonium chloride and slaked lime and heat gently in 
the generating flask in the hood, collecting the gas in the flask of 
the fountain apparatus. 

Fill the medicine dropper with water, and the glass dish with 
the red litmus solution. 
From time to time hold 
an open bottle of concen- 
trated hydrochloric acid 
near the mouth of the 
inverted flask, and when 
a heavy cloud of white 
fumes is observed, insert 
the rubber stopper and 
transfer the flask to its 
position in the retort 
stand of the fountain ap- 
paratus. Press the bulb 
of the medicine dropper 
so as to force a few drops 
of water into the appa- 
ratus. These few drops 
dissolve practically all 
the ammonia in the flask, 
thus creating a vacuum, 
into which the water is 
then forced by the pres- 
sure of the air on the 
water in the dish. Note 
also the effect of the 
ammonia on the litmus. 
What does this indicate ? 



Ammonia gas is enor- 
mously soluble in water. 
One gallon of water 
will absorb about 700 
gallons of ammonia, or 
about one half its own 
weight of the gas. Thus about one third of the weight of 
the strongest ammonia water consists of the gas, and the 

K 




Fig. 38. — Experiment 74. Fountain apparatus. 



130 ELEMENTARY HOUSEHOLD CHEMISTRY 

water constitutes the other two thirds. For ordinary house- 
hold use much weaker solutions than this are sold. Com- 
mercial " household ammonia ".sometimes contains impurities 
which fade colors or cause white materials to turn yellow. 
It will be found safer and more economical to buy concen- 
trated ammonia from a druggist, dilute it with its own vol- 
ume of water, and keep it in bottles carefully closed with 
glass or rubber stoppers. This solution can be further diluted 
with three times its own volume of water for most house- 
hold uses. In pouring ammonia water from bottle to bottle 
discomfort can be avoided by holding the bottles above the 
level of the eyes. The escaping gas, being lighter than air, 
ascends. 

The Ammonium Radicle 

Ammonia water has an alkaline reaction, and, like the 
hydroxides of metals, neutralizes acids, producing salts. 
These facts lead us to infer that when ammonia gas dissolves 
in water, it combines with the water, forming a hydroxide. 

Ammonia -f- Water = Ammonium hydroxide 
NH 3 + H 2 = NH 4 OH 

The base would thus be the hydroxide of a radicle, NH 4 — , 
made up of nitrogen and hydrogen. To this radicle the 
name " ammonium" is applied. The same radicle is present 
in all ammonium salts, e.g. ammonium chloride (sal am- 
moniac) NH4CI, ammonium sulphate (NEL^SO^ and am- 
monium carbonate (smelling salts) (NH 4 ) 2 C03. In their 
solubilities the ammonium salts are very similar to the corre- 
sponding salts of potassium. 

To include ammonium hydroxide among the bases we may 
expand our definition of a base (see p. 94) into the fol- 
lowing : 

A base is the hydroxide of a metal or of a radicle which plays 
the part of a metal. 



AMMONIA AND THE AMMONIUM RADICLE 131 

Ammonium hydroxide is said to be a " volatile " alkali, 
because it evaporates without leaving a residue. This prop- 
erty gives it an advantage over " fixed " alkalies, such as 
sodium hydroxide or sodium carbonate, for many purposes, 
such as the washing of window panes and the neutralization 
of acid stains on fabrics. 

Ammonium carbonate gradually liberates ammonia and 
carbonic acid gases at ordinary temperatures and, therefore, 
smells strongly of ammonia. It is the basis of " smelling 
salts," which, as a rule, contain also some other fragrant 
substance, such as lavender. Ammonium carbonate is 
popularly known as " crystal ammonia." Mixtures of soda 
with just enough ammonium carbonate to impart an odor 
are sometimes fraudulently sold as " solid household am- 
monia." 

Experiment 75. 

Heat a small quantity (| gram) ammonium carbonate in a 
porcelain dish. What becomes of the substance? How could 
one detect soda as an adulterant of crystal ammonia? 

EXERCISES 

1. Write equations for the reactions obtained in Experiment 73. 

2. Write equations for the reaction of ammonia gas with 
(a) hydrochloric acid, (b) nitric acid, (c) sulphuric acid, (d) acetic 
acid, (e) carbonic acid. 

3 . Write equations representing the neutralization of ammonium 
hydroxide by (a) hydrochloric acid, (b) sulphuric acid, (c) nitric 
acid, (d) acetic acid. 



CHAPTER XXIV 

ORGANIC RADICLES. HYDROCARBONS AND 
ALCOHOLS 

The compounds of the element carbon (with the exception 
of carbon monoxide, carbon dioxide, and the carbonates) 
are called organic compounds. Many of them are found in, 
or made from, animal and vegetable organisms, arid it was 
formerly believed that they could not be made without 
the agency of life. This is now known to be untrue for many 
of them, but the term " organic " is still applied to the 
branch of chemistry which treats of the very numerous com- 
pounds of this one element, carbon. 

Among the compounds of carbon there are many instances 
of radicles existing as the common constituents of a number 
of compounds, much in the same way as the ammonium 
radicle, NH 4 — , exists in all the ammonium salts (see p. 130), 
or as an acid radicle exists in an acid and all its salts (see p. 86). 
These organic radicles may consist of carbon and hydrogen 
in various proportions ; of carbon, hydrogen, and oxygen ; of 
carbon, hydrogen, and nitrogen ; etc. 

Among the simplest and most frequently occurring or- 
ganic radicles are the hydrocarbon radicles, consisting of 
carbon and hydrogen only. Many of these can be arranged 
in classes or series in which each member differs in formula 
from the preceding one by one atom of carbon and two atoms 
of hydrogen. 

Thus we have, as one important series : 

The methyl radicle, CH3 — 
The ethyl radicle, C 2 H 5 — 
The propyl radicle, C 3 H 7 — 
The butyl radicle, C4H9 — 
The amyl radicle, C 5 Hu — 
etc., etc. 
132 



ORGANIC RADICLES 



133 



The compounds of the radicles of such a series with any 
element, or with any other radicle, have certain points of 
similarity, and there is a gradual variation in properties from 
the compounds at one end of the series to those at the other 
end. For example, the compounds of the above radicles 
with hydrogen are substances which resist the action of many 
of the reagents (such as chlorine, nitric acid, and sulphuric 
acid) which act readily on other compounds of carbon and 
hydrogen. For this reason they are called the paraffins 
(Latin, parum affinis, possessing little affinity). Petroleum 
and its commercial products — benzine, gasoline, kerosene, 
and paraffin wax — are mixtures of the higher compounds 
of this series. Natural gas (see Chapter XII) consists chiefly 
of the first member of the series, — methane, CH 4 , — but also 
contains a little ethane, C 2 H 6 , and smaller quantities of a 
few of the other members of the series. The following table 
of the densities and boiling points of a few members of this 
series will illustrate how the properties of the compounds 
gradually change from one end of the series to the other. 



Name 


Formula 


Density as a 
Liquid 


Boiling Point 


Methane 


CH4 


.42 


-164 


Ethane 


C2H6 


•45 


- 93 


Propane 


C3H8 


•54 


- 38 


Butane 


C4H10 


.60 


+ 1 


Pentane 


C 5 H 12 


•63 


+ 37 • 


Hexane 


C&tLu 


.66 


+ 69 



At ordinary room temperature (20 C.) the first four 
members of this series are gases, those with 5 to 10 carbon 
atoms to the molecule are liquids, and the higher members 
of the series solids. One has been made with 60 carbon 
atoms to the molecule, i.e. C 60 Hi 2 2. It is a solid, melting 
at about the boiling point of water. 



134 



ELEMENTARY HOUSEHOLD CHEMISTRY 



Alcohols 

When yeast is allowed to grow in grape juice or in the 
" wort " obtained by extracting malt with water, the sub- 
stance called alcohol (or grain alcohol) is produced. This 
substance is the characteristic intoxicating constituent of all 
liquors. When obtained pure, it is exactly the same sub- 
stance whether it comes from cider, wine, beer, or whisky. 

A similar but distinct substance is obtained as one of 
the products of the " dry " distillation of wood (heating the 
wood in closed retorts and cooling the vapors evolved). 
This substance is known as wood alcohol in contradistinction 
to grain alcohol. (Cf. pp. 41 and 67.) 

Still other allied substances are produced in very small 
quantities along with grain alcohol in the fermentation of 
the sugar of fruit juices or malt wort. These constitute the 
fusel oil which is separated from grain alcohol in the process 
of distillation (which consists in boiling the liquid and recon- 
densing the vapors to liquid by cooling). 

To all the compounds of this class the general term alcohols 
is applied. They are all found to be hydroxides of hydro- 
carbon radicles. The alcohols of the radicles given above 
constitute the following series : 



Formula 


Name 


Density 


Boiling Point 


CH3OH 


Methyl alcohol 
(wood alcohol) 


.812 


66° C. 


C2H5OH 


Ethyl alcohol 
(grain alcohol) 


.806 


78 


C3H7OH 


Propyl alcohol 


.817 


97 


C 4 H 9 OH 


Butyl alcohol 


.823 


117 


C 5 HnOH 


Amyl alcohol 


.829 


138 



As in the case of the hydrocarbon series, the density and 
boiling point of each member of the series are higher than 



ORGANIC RADICLES 135 

those of the preceding compound. There is, however, an 
exception in the density of ethyl alcohol, as compared with 
that of methyl alcohol. 

In that they are hydroxides, the alcohols resemble the 
bases. In most respects, however, there is a marked differ- 
ence between the alcohols — the hydroxides of hydrocarbon 
radicles — on the one hand, and the bases — the hydroxides 
of metals or metal-like radicles — on the other hand. All 
the alcohols are neutral in reaction ; while all soluble bases 
are alkaline. The simpler alcohols, e.g. all those listed 
above, are liquids, and so are some of the more complex 
compounds of this class ; while the simpler bases, i.e. the 
hydroxides of the metals, are solids, and only the more 
complex bases, e.g. hydroxides of metal-like radicles such as 
ammonium NH 4 — , aniline C 6 H 5 NH 3 — , etc., are liquids, or 
exist in the dissolved form in water. Alcohols do not ionize 
when dissolved in water ; bases do. 

Experiment 76. 

Examine specimens of pure methyl alcohol, pure ethyl alcohol, 
and amyl alcohol. Note odor of each and effect on litmus paper, 
red and blue. Determine for each whether it is completely mis- 
cible with water. 

Glycerol 

Just as there are bases with more than one hydroxyl group, 
— OH, in the molecule, e.g. Ca(OH)2, Al(OH)s, so also there 
are alcohols with more than one hydroxyl group. The most 
important of these, in relation to household chemistry, 
is glycerol, known commercially as glycerin or glycerine. 
Glycerol is the hydroxide of the trivalent radicle glyceryl, 
C3H5 =. Its formula is C 3 H 5 (OH) 3 . 

Experiment 77. 

Examine a specimen of glycerin (commercial glycerol). Note 
its viscosity, miscibility with water, taste, and effect on red and 
blue litmus paper. 



136 ELEMENTARY HOUSEHOLD CHEMISTRY 

Structural Formulas 

In organic chemistry it is a common thing for several 
compounds to contain the same elements in the same pro- 
portions. Thus we have three different sugars with the 
formula C12H22O11 — cane sugar, milk sugar, and malt sugar. 
Such compounds are said to be isomers, or isomeric compounds. 
In many instances we are able to distinguish isomers from 
one another by representing their atoms as differently joined 
in the molecule. Thus the formula, C2H 6 0, represents two 
compounds, viz. ethyl alcohol and dimethyl ether. These 
are distinguished as follows : 

H H 

M— C— H H— C— H 

H— C— O— H O 

H H— C— H 

I 
or C2H5OH, H 

Ethyl alcohol 

or (CH 3 ) 2 

Dimethyl ether 

Ethyl alcohol is the hydroxide of the ethyl radicle, while 
dimethyl ether is the oxide of the methyl radicle. In the 
former the two carbon atoms are represented as joined di- 
rectly together and the oxygen atom as connecting one of the 
hydrogen atoms to a carbon atom. In the latter all six 
hydrogen atoms are joined directly to carbon, and the oxygen 
atom unites the two carbon atoms. 

Formulas of this kind are called structural or graphic 
formulas. 

The structural formulas of all alcohols have the hydroxyl 
group, — OH, joined to a carbon atom to which no other 
oxygen atom is attached. 



ORGANIC RADICLES 137 

The following are the structural formulas of methyl 
alcohol and glycerol. 



H 




H 


H— C— 0- 

1 


-H 


H— C— 0— H 


1 
H 




H— C— 0— H 


or CH3OH, 

Methyl alcohol 




H— C— 0— H 

1 
H 

or C 3 H5(OH) 3 , 
Glycerol 



It will be noted that in all these formulas the carbon 
atom is represented as having four valence bonds, the oxygen 
atom two, and the hydrogen atom one ; thus : 
1 
— C— — O— and H— 

I 



CHAPTER XXV 
ESTERS. FATS 

In their behavior towards acids, alcohols resemble, but 
differ from, bases. It will be remembered that a base reacts 
with an acid to give water and a product called a salt. Sim- 
ilarly, an alcohol reacts with an acid to give water and a 
product analogous to a salt. For instance 

Base + Acid = Salt + Water 

Sodium hydroxide + Acetic acid = Sodium acetate + Water 
NaOH + CH3COOH = CH 3 COONa + H 2 

So also 

Alcohol + Acid = Ester + Water 

Ethyl alcohol + Acetic acid = Ethyl acetate + Water 
C2H5OH + CH3COOH = CH 3 COOC 2 H 5 + H 2 

Thus the esters bear the same relation to acids and alcohols 
that salts bear to acids and bases. The ester is obtained 
from the acid by the replacement of the hydrogen of the acid 
by the radicle of the alcohol. In their physical properties, 
however, esters are no more like salts than alcohols are like 
bases. Ethyl acetate and other esters of the simpler alcohols 
with the simpler organic acids are neutral, volatile liquors, 
with pleasant fruity odors. They are nearly insoluble in 
water and do not ionize when dissolved. The flavors and 
odors of fruits and wines are in part due to the esters they 
contain. Some esters are manufactured and sold as flavor- 
ing matters or perfumes. Amyl acetate, for example, is 
sold as pear oil, methyl butyrate as pineapple oil, etc. 
Esters of more complex alcohols and acids are important 
constituents of the waxes — beeswax, Carnauba wax, etc. 

138 



ESTERS. FATS 139 

Experiment 78. 

Examine specimens of methyl acetate, ethyl acetate, propyl 
acetate, amyl acetate (pear oil), methyl butyrate (pineapple oil), 
ethyl citrate, methyl salicylate (oil of wintergreen) . 

The reactions between alcohols and acids are much slower 
than those between bases and acids. When ethyl alcohol and 
acetic acid are mixed and kept at ordinary room tempera- 
ture, the formation of ethyl acetate goes on slowly for several 
months. If the mixture is kept hot, the reaction goes on 
more rapidly. There are also certain substances, such as 
sulphuric acid, which will accelerate the action. A common 
method of preparing esters is to mix the alcohol with sul- 
phuric acid, add the acid whose ester is wanted, and distill 
out the ester. 

Experiment 79. 

Mix equal volumes of alcohol and concentrated sulphuric acid. 
Add acetic acid and boil. Note the odor and compare with those 
of alcohol, acetic acid, and ethyl acetate. Has ethyl acetate been 
formed ? Write equations for the reaction (omitting the sulphuric 
acid from the equation). 

Fats 

The esters of the alcohol, glycerol, with certain organic 
acids, constitute the fats. Natural fats and animal and 
vegetable oils — lard, tallow, butter, lard oil, olive oil, 
cottonseed oil, linseed oil, castor oil, etc. — are mixtures 
of the glycerol esters of a number of different acids. 

The most common of these acids are palmitic, HCi 6 H 31 2 , 
a soft solid ; stearic, HC18H35O2, a soft solid ; and oleic t 
HC18H33O2, a liquid. 

The most common simple fats are therefore : 

Glyceryl palmitate, CsH^deHsiC^ known as palmitin or 
tripalmitin. This, like palmitic acid, is a solid. 

Glyceryl stearate, CsH^CigHssCWs, stearin or tristearin — 
also a solid. 



140 ELEMENTARY HOUSEHOLD CHEMISTRY 

And glyceryl oleate, C 3 H5(Ci 8 H 3 302)3, olein or triolein — 
a liquid. 

Experiment 80. 

Examine specimens of palmitic, stearic, and oleic acids, and of 
the three simple fats, tripalmitin, triolein, and tristearin. 

The structural formula of ethyl acetate is CH 3 COOC 2 H 5 , 
or 

H H H 

I /O I I 
H— C— C^-O— C— C— H, 

H H H 

that of acetic acid being CH3COOH, or 

H 

H— C— C^-O— H 

I 
H 

Palmitic and stearic acids belong to the same series of 
acids as acetic acid. In structure they differ from acetic 
acid in having a long chain of carbon atoms (each carrying 
two hydrogen atoms) between the carbon atom of the CH 3 — ■ 
radicle and that of the — COOH radicle. 1 Palmitic acid has 
14, stearic acid 16, of these intermediate carbon atoms in its 
chain. 

Tripalmitin may, therefore, be represented by the follow- 
ing structural formula : 

CH 3 • (CH 2 )i4 • C^-O— C-H 

/O I 
CH3 • (CH 2 )i4 • C^-O—C— H 

CH 3 • (CH 2 )« • C^-O— C— H 

1 The — COOH radicle, called carboxyl, is the characteristic radicle of organic 
acids. 



ESTERS. FATS 141 

and tristearin by a formula differing from this in having 16 
CH 2 's instead of 14. 

The structural formula of oleic acid, which contains two 
hydrogen atoms less than stearic acid, is : 

CH 3 (CH 2 ) 7 • CH=CH • (CH 2 ) 7 COOH 

that is to say, the middle carbon atoms of the molecule are 
joined by two bonds instead of one. 

The structural formula of triolein, therefore, resembles 
that of tripalmitin given above, except that two — CH='s 
are inserted between the seventh and eighth of the chain of 
CH 2 's. 

It will be readily understood that fats may also be derived 
from the reaction of two or three acids with glycerol. Thus 
we might have an oleo-stearo-palmitin, derived from three 
fatty acids. Its formula would be : 

CH 3 (CH 2 ) 7 - CH=CH(CH 2 ) 7 C^O— C— H 
CH 3 (CH 2 ) 16 C^O— C— H 
CH3(CH 2 ) 14 C^-0— C^-H 

" Mixed " esters of this type are actually found in natural 
fats. Butter, for instance, has been shown to contain a fat 
which is an ester of palmitic, oleic, and butyric acids, the last- 
mentioned being an acid of the same series as acetic, palmitic, 
and stearic, viz. CH 3 (CH 2 ) 2 COOH. 

The natural fats are mixtures of these various compounds, 
and owe their physical differences to differences in the pro- 
portions of the individual glycerides which they contain. 
The oils and more liquid fats (e.g. lard) contain larger pro- 
portions of olein, the more solid fats (e.g. tallow) smaller 
proportions of olein and larger proportions of stearin and 
palmitin. Some of them, such as butter, castor oil, linseed 



142 ELEMENTARY HOUSEHOLD CHEMISTRY 

oil, etc., also contain material quantities of the glycerol 
esters of other acids than palmitic, stearic, and oleic. 

Even the fat of two animals of the same species may 
differ if the two have been on different diets. The bacon 
from hogs fed on oats, peas, and barley is firmer than that 
from hogs fed on Indian corn and beans. When the fat of 
the firm bacon and that of the soft bacon are analyzed, it is 
found that the former contains a larger proportion of stearin 
and palmitin than the latter. In one investigation the fat 
from soft bacon was found to contain four times as much 
olein as stearin and palmitin together, while the fat of firm 
bacon had only about twice as much olein as stearin and 
palmitin. 



CHAPTER XXVI 

HYDROLYSIS OF ESTERS. SAPONIFICATION 

Hydrolysis of Esters. — We have seen (Chapter XXI) 
that the reaction by which salts and water are formed from 
weak acids and bases is to some extent reversible — the salts 
reacting with water to form acids and bases. This reaction 
of salts with water we have called the hydrolysis of the salt. 

Esters are subject to hydrolysis to even a greater extent 
than salts. The products of such hydrolysis are, of course, 
acids and alcohols, e.g. : 

Ethyl acetate + Water = Ethyl alcohol + Acetic acid 
CH 3 COOC 2 H 5 + H 2 = C 2 H 5 OH + CH 3 COOH 

The rate at which esters react with water is, however, 
small, unless there is present some substance which has the 
power of accelerating the reaction. The acids are one class 
of substances possessing this accelerating power, particularly 
the strong acids, such as hydrochloric and sulphuric. In 
accelerating hydrolysis these acids are not themselves 
changed, and we do not understand why they influence the 
rate of hydrolysis of esters. But the fact that they do so is 
well established. 

Another class of substances having a similar effect — ■ 
particularly upon the hydrolysis of fats — is the class known 
as lipases, a special division of a more general class of sub- 
stances, known as ferments or enzymes. Ferments are organic 
substances possessed of the power of promoting reactions be- 
tween other substances without being themselves destroyed. 

143 



144 ELEMENTARY HOUSEHOLD CHEMISTRY 

Ferments are secreted, some of them by microorganisms, 
others by plants, and still others by special organs (glands) of 
the bodies of the higher animals. A ferment of the lipase 
class (sometimes called steapsin) is present in the digestive 
juices which act upon foods in the small intestine. It has the 
power of " splitting " fats ; that is to say, of causing them to 
react with water to yield fatty acids and glycerol. Though the 
digestion of fats is not thoroughly understood, it is believed 
that they are thus hydrolyzed in the intestine, and that the 
acids and glycerol, after passing into the intestinal wall, are 
recombined to build up the fat of the body. In this recom- 
bination, the proportions of olein, palmitin, stearin, and 
" mixed " esters formed are not always the same as those 
originally present in the fat of the food, since the animal may 
take apart the fats of its food and reconstruct them into the 
fats peculiar to its own species. On the other hand, when an 
animal is fattened rapidly on fatty food, the food fat may be 
deposited in the adipose tissues without loss of its chemical 
characteristics. 

Saponification 
Experiment 81. 

Materials : 
Ethyl acetate. 

Dissolve a few drops of ethyl acetate in half a test-tubeful of 
water. If not all the ethyl acetate added mixes with the water 
on shaking, add more water until a clear solution is obtained. 
Divide the solution into three exactly equal parts in three test 
tubes of equal diameter. Into the test tubes put respectively, 
(i) \ cc. dilute sulphuric acid, (2) exactly the same volume of 
the reagent sodium hydroxide solution, (3) exactly the same 
volume of water. Label the three test tubes and place them, 
side by side, in a beaker of water which feels just warm to the 
hand. Allow to stand, comparing the odors of the three every 
five minutes. From which tube does the odor of ethyl acetate 
disappear first? What do you infer as to the effect of sodium 
hydroxide in promoting the hydrolysis of ethyl acetate? How 
does it compare with sulphuric acid in this respect? 



HYDROLYSIS OF ESTERS. SAPONIFICATION 145 

When an ester is treated with a strong base (alkali), it 
reacts with the base, forming a salt and a free alcohol. 

Ester + Base = Salt + Alcohol 

e.g. Ethyl + Sodium = Sodium + Ethyl 

acetate hydroxide acetate alcohol 

CH3COOC2H5 + NaOH = CH 3 COONa + C 2 H 5 OH 

This reaction may be compared with that of a strong base 
on an ammonium salt, e.g. that of sodium hydroxide with 
ammonium chloride : 

NH4CI + NaOH = NaCl + NH 4 OH 

the sodium salt of the acid being formed and the weak 
base liberated. It may also be regarded as a combination 
of hydrolysis and neutralization. As fast as any free acetic 
acid is formed by the hydrolysis of the ester 

CH 3 COOC 2 H 5 + H 2 = CH3COOH + C2H5OH 

it is neutralized by the alkali, 

CH3COOH + NaOH = CH 3 COONa + H 2 

The effect of thus immediately removing the acid by neu- 
tralization is to accelerate the hydrolysis greatly and also 
to allow the hydrolysis to become complete, the whole of the 
ethyl acetate being used up, which is not the case when the 
ester is hydrolyzed alone. ' 

When the ester is a fat, the salt formed by action of the 
base is a soap. Thus 

Fat + Base = Soap + Glycerol 

Glyceryl palmi- + Sodium = Sodium palmi- + Glycerol 
tate hydroxide tate 

(C 15 H 31 COO)3C 3 H 5 + 3 NaOH = 3 C 15 H 31 COONa + C 3 H 5 (OH) 3 

This is saponification (soap making) proper, but the term 
has been extended in meaning so as to include the reaction 
of any ester with a base. Hence we speak of the saponifica- 
tion of ethyl acetate as well as that of lard or tallow. 



146 ELEMENTARY HOUSEHOLD CHEMISTRY 

Soaps 
Experiment 82. 

Materials : 

Lard. 

10 per cent solution of potassium hydroxide in alcohol. 

Flask, 150 cc. 

Evaporating dish, 6 inch. 

Water bath. 
Weigh out 25 grams lard and introduce it into the flask. Add 
75 cc. alcoholic potash. Heat on a water bath until a drop let 
fall into water dissolves clear, i.e. without leaving any globules of 
fat. Place 100 cc. water in the evaporating dish and pour the 
contents of the flask into the dish. Place on the water bath and 
evaporate until the odor of alcohol is gone and a pasty residue 
remains. Redissolve this residue in hot water. Note the feel 
of this solution. To a small portion add calcium chloride solution. 
Save the main portion for Expt. 83, and a small one for Expt. 84. 

Experiment 83. 

, Materials : 

Sodium carbonate, powdered. 
Potassium bisulphate, powdered. 

Place a piece of litmus paper in the solution saved from Experi- 
ment 82 and acidify with dilute hydrochloric acid. Note what 
rises to the surface. This precipitate consists of a mixture of the 
fatty acids, the salts of which constitute the soap. Write equa- 
tions for the reaction of hydrochloric acid with potassium palmitate. 

Boil the liquid and filter through a wet filter. The fatty acids 
do not pass through the wet filter. To the filtrate add powdered 
sodium carbonate, little by little, stirring, until the acid is neu- 
tralized. Evaporate to dryness. Allow to cool. Stir up the 
residue with alcohol, filter, and evaporate the alcohol on the water 
bath. 

Examine the sirupy residue. Mix a drop or two with powdered 
potassium bisulphate and heat in a test tube, noting odor. Make 
the same test on glycerol, comparing results with those obtained 
with the residue. The odor produced by heating glycerol with 
potassium bisulphate is that of a substance called acrolein, C3H4O. 
This is one of the products of a decomposition of glycerol, the other 
being water : 

C 3 H 8 3 = C3H4O + 2 H 2 



HYDROLYSIS OF ESTERS. SAPONIFICATION 147 

The chemical reaction involved in the manufacture of 
soap is that given above (p. 145), viz. : 

Fat + Base = Soap + Glycerol 

For the preparation of soft soaps the base used is potassium 
hydroxide ; for the hard soaps, sodium hydroxide. 

The fat may be boiled with an aqueous solution of the base, 
or the two may be put together and either left standing for 
several days or subjected to pressure for a shorter space of 
time. 

Soaps made by the latter method (the " cold process ") 
contain the glycerol produced in the reaction. Glycerol, 
being an emollient, healing substance, is an unobjectionable 
constituent of toilet soap. In the boiling process it is more 
common to separate the soap and glycerol by " salting out " 
the former. When the saponification is complete, common 
salt is added to the pot. The soap, being insoluble in salt 
solutions, is precipitated and collects on the surface of the 
water. Soap made in this way is known as " curd " soap. 

Experiment 84. 

Heat a soap solution until it is quite clear. Add solid sodium 
chloride. Note what separates from the liquid. Allow this pre- 
cipitate to collect at the surface of the liquid. Pour or skim off 
into a test tube, add distilled water, and warm. Does it dissolve? 

In what respect does the effect of sodium chloride on a soap 
solution differ from that of calcium chloride? Sodium sulphate 
has an effect similar to that of sodium chloride. Explain why 
permanently hard water softened with soda is not quite as satis- 
factory for laundry purposes as naturally soft water. 

The glycerol, which is left in solution in the brine in this 
" boiling process " of soap making, is subsequently refined 
and sold as " glycerin " for medicinal use or for the manu- 
facture of explosives, — nitroglycerin, dynamite, etc. 

In the manufacture of soft soap it is customary to leave 
the glycerol in the soap. 



CHAPTER XXVII 
COMMERCIAL SOAPS 

The chemical reactions involved in the manufacture 
of soap conform, of course, to the law of definite proportions. 
(See Chapter VII.) To saponify a given weight of a pure 
fat, e.g. glyceryl palmitate, a definite weight of a pure base, 
e.g. sodium hydroxide, is required. If too much fat is used, 
the excess will be left in the soap as " unsaponified' fat." 
If too much base is used, the excess will remain in the soap 
as " free alkali." Moreover, since saponification is a rather 
slow process, it is quite possible for a soap to contain both 
free alkali and unsaponified fat, if time has not been allowed 
for the reaction to run to completion. Since all natural 
fats are mixtures and the commercial alkalies used in soap 
manufacture are not chemically pure substances, it requires 
great skill and care to manufacture soap which is free from 
both unsaponified fat and free alkali. For rough cleaning 
purposes, such as scrubbing, an excess of free alkali can be 
tolerated, and soap suitable for such purposes may be made 
at home. On painted or varnished surfaces soaps should 
be used with extreme care, if at all. If used, they should 
contain no free alkali. Scouring powders and soaps contain- 
ing much free alkali are injurious to aluminium ware. For 
laundry purposes, except for woolens or silks, a little free 
alkali is permissible, but the amount should not be as much 
as one per cent of the weight of the dry soap. Toilet soaps 
and wool soaps should not contain any free alkali. Laundry 
soaps should not contain any unsaponified fat. 

148 



COMMERCIAL SOAPS 149 

Experiment 85. — Test for Unsaponified Fat. 

Materials : 

A number of samples of commercial and home-made soaps. 

Benzine. 

An alcoholic solution of the dye Sudan III. 
Finely slice about 5 grams of the soap. Spread on a watch 
glass and dry in a water oven. Place half the dried residue in a 
test tube, cover with benzine, and shake for some time. Filter 
off the benzine through a dry filter on to a clean watch glass and 
allow it to evaporate. Evaporation may be hastened by placing 
the watch glass on a steam radiator or on a steam bath. A smeary 
residue is an indication of fat. To confirm, add a little of the 
Sudan III solution, and stir with the smeary residue. Pour off 
the Sudan III from the watch glass, wash once with alcohol, and 
add hot water. Globules of fat, colored pink with the dye, will 
float on the water. 

Experiment 86. — Test for Free Alkali 

Materials : 

Soaps used in Experiment 85. 
Phenolphthalein solution. 
Shake a portion of the fresh soap with alcohol and add a drop 
or two of the phenolphthalein solution. A pink color shows the 
presence of free alkali. 

Why may not the soap be dissolved in water for this test? 
(See Chapter XXI.) 

All commercial soaps contain more or less water. A 
well-made soap should not contain over 25 per cent. Low- 
grade soaps sometimes contain 35 per cent or even more ; 
good toilet soaps sometimes as low as 13 to 15 per cent. 

Experiment 87. — Determination of Water Content. 

Materials : 
Soap. 

100 cc. beaker. 
Sand. 

Water bath. 

Air bath with thermometer. 
In an evaporating dish heat enough of the sand to cover the 
bottom of the beaker to the depth of half an inch. Allow to cool. 



150 ELEMENTARY HOUSEHOLD CHEMISTRY 

Shave all the soap finely, mix well, and weigh out 5 grams. 
Place the sand and a glass stirring rod in the beaker and determine 
the weight. Add the soap and 25 cc. or more alcohol. Heat on 
the water bath, stirring well to dissolve the soap in the alcohol. 
Evaporate to dryness on the water bath, then place in the air 
bath and regulate the flame so as to keep the temperature con- 
stant at no° C. After one hour remove the beaker from the air 
bath, allow to cool, and weigh. Return the beaker to the air 
bath for half an hour. Cool again and weigh. Repeat until 
constant or nearly constant weight is attained. Calculate what 
percentage of water the soap contained. 

Not only is the quantity of water contained in a soap of 
interest in relation to the price, but it is also of importance 
with reference to the lasting quality of the cake or bar. 
Moist soap is soft and tends to waste in use. The drying 
of soap is, therefore, a good household practice. The bars 
should be cut into pieces of convenient size for use and kept 
in a warm place, piled loosely, so as to allow a free circulation 
of air. 

Although soda soaps are all classed as " hard," there is 
actually a great deal of variation in the hardness of different 
samples. The hardness depends to some extent, as we have 
just seen, on the proportion of water in the soap. It also 
depends on the materials from which the soap was made. 
Soaps containing too much oleate will be soft and soluble. 
Thus, soaps made from olive or cottonseed oil lather better, 
but waste away more rapidly than those made from the 
solid fats, palm oil and tallow, which contain a larger propor- 
tion of stearate and palmitate. 



CHAPTER XXVIII 
FOREIGN INGREDIENTS OF COMMERCIAL SOAPS 

We have seen that in addition to the soaps proper — i.e. 
the salts of fatty acids — commercial soaps always contain 
water and may contain glycerol, unsaponified fat, and free 
alkali. But in practice other substances are frequently 
added, either to lower the cost of production or to render the 
soap more attractive. The substances added to lower the 
cost of production are of two classes: (i) other detergents; 
(2) fillers. 

Detergents 

Among the detergents added to soaps are : 

Sodium and Potassium Carbonates. — These are cheap 
and harsh alkalies and are to be regarded as adulterants, 
except in soaps to be used for rough cleaning. Even for 
such purposes the soda or potash can be more economically 
purchased separately, as soda ash or washing soda, and as 
pearl ash, respectively. Sodium carbonate cannot be added 
to soap in greater quantity than 5 per cent without causing 
a white incrustation on the surface of the soap. Potassium 
carbonate can be added in larger quantity, and has the prop- 
erty of making the soap look finer in texture and therefore 
more attractive. 

Experiment 88. — Test for Carbonates 

Materials : 

Soda ash (sodium carbonate). 
Pearl ash (potassium carbonate). 
Commercial soaps and washing powders. 
Add a little dilute sulphuric acid to (1) soda ash, (2) pearl ash. 
Note and account for the effervescence. Write equations for the 
reactions. 



152 ELEMENTARY HOUSEHOLD CHEMISTRY 

Test the commercial soaps and washing powders for carbonates 
in the same way. 

Sodium silicate is known as " water glass." This substance 
gives firmness to soap, and enables it to hold more water and 
still remain hard. In small quantities it is a legitimate ad- 
dition to soaps for some purposes. Soaps containing more 
than a very little silicate, when used in the laundry, leave a 
deposit of silica (an insoluble substance of the same composi- 
tion as sand) in the clothes. 

Experiment 89. — Test for Silicate. 

Treat the finely shaved soap with hot alcohol until nothing 
further dissolves ; filter and wash with hot alcohol. Now wash 
the residue with hot water, collecting the solution obtained. 
Acidify this solution with hydrochloric acid, evaporate to dryness, 
and gently heat the residue for some time. If it. chars, heat more 
strongly until it is completely burned. Allow to cool, add water 
and a little hydrochloric acid, and warm. Silica will be left as an 
insoluble, gritty residue. 

Sodium Resinate. — Rosin (also termed colophony) consists 
of acids which react with alkalies to form salts called resinates, 
which, like soaps, have detergent properties. These resi- 
nates cannot be used separately for cleansing purposes. In 
dilute hot solutions they hydrolyze to so great an extent as 
to precipitate the rosin acids. These are deposited on the 
goods, causing a yellow stain having the odor of rosin. Resi- 
nates are often contained in laundry soaps, particularly yellow 
soaps, and are objectionable constituents, unless present 
in only small quantities. Yellow soaps have been analyzed 
which contain up to 40 per cent of resinates. Soaps con- 
taining resinates are sometimes called " rosin soaps " and are 
spoken of as containing rosin. 

Experiment 90. — Test for Rosin. 

Materials : 

Soaps with and without rosin. 
Acetic anhydride. 



FOREIGN INGREDIENTS OF COMMERCIAL SOAPS 153 

Compare the odors of the soaps containing rosin with the odors 
of the non-rosin soaps. Dissolve the soaps in water. Acidify 
with sulphuric acid. Filter. Dissolve the precipitate in acetic 
anhydride. What is this precipitate (1) if the soap is pure? 
(2) if the soap contains rosin? 

To 5 cc. water add 5 cc. concentrated sulphuric acid. Cool 
the mixture. Place about 2 cc. in a test tube and add a few 
drops of the acetic anhydride solution of the fatty acids. A 
violet coloration shows that rosin is present. 

Petroleum Products. — Petroleum products, such as paraf- 
fin wax, kerosene, and naphtha (a volatile product resembling 
benzine) are sometimes added to soap. These, being fat 
solvents, have value as detergents. Kerosene itself is some- 
times used in the clothes boiler, both in the household and in 
commercial laundries. The naphtha soap, however, cannot 
be used with hot water. 

Borax is a sodium borate, whose detergent property is 
well known. It is an excellent ingredient of soaps. 

Fillers 

Among the " fillers," i.e. cheap, weight-making substances 
of little or no detergent value, used as ingredients of commer- 
cial soaps, are the sulphates of sodium, potassium, calcium, 
and barium, infusorial earth (a fine form of silica, Si02, left 
from the decay of minute marine organisms called infusoria), 
fine clay, chalk, or whiting (calcium carbonate), French chalk 
(a soft, powdery magnesium silicate), starch, and impure 
vaseline. In the detection of these substances advantage is 
taken of the circumstances that none of them is soluble in 
alcohol and only the sodium sulphate and potassium sul- 
phate are soluble in water. 

Experiment 91. — Tests for Fillers. 

Dissolve the finely shaved soap in alcohol. Filter and wash 
the insoluble residue with alcohol, rejecting the alcoholic solution. 
Boil the residue insoluble in alcohol with water. Treat the residue 
insoluble in water and the water solution as follows: 



154 



ELEMENTARY HOUSEHOLD CHEMISTRY 



Residue 



Solution 



Acidify with dilute hydro- 
chloric acid. Effervescence in- 
dicates a carbonate such as 
chalk or whiting. 

Residue insoluble in dilute 
acid may be calcium sulphate, 
barium sulphate, silica, clay, 
French chalk, etc. 



Acidify with dilute hydrochlo- 
ric- acid. Effervescence shows 
presence of sodium or potassium 
carbonate. 

To a portion of the acidified 
solution add barium chloride. A 
white precipitate, insoluble in 
acids, shows the presence of 
sodium or potassium sulphate. 

Cool a portion of the acidified 
solution and add iodine. A blue 
color shows starch. 



CHAPTER XXIX 

SPECIAL SOAPS AND SCOURING POWDERS 

Perfumed and Colored Soaps. — The perfumes and color- 
ing matters ordinarily added to toilet soaps are harmless, 
but sometimes excessive quantities of perfume are used to 
conceal disagreeable odors due to the use of decomposing 
fats. Strongly perfumed soaps are, therefore, to be regarded 
with suspicion. 

Transparent Soaps. — The best transparent soaps are 
made by dissolving the soap in alcohol, filtering off the un- 
dissolved residue, then removing the alcohol by evaporation. 
Glycerin is often added to give a pleasant emollient feel. 
Cheaper transparent soaps are made by the cold process 
from tallow, castor oil, palm oil, or coconut oil. These 
usually contain free alkali. Some contain sugar, an unde- 
sirable adulterant, because, being so soluble, it causes rapid 
wasting of the soap. 

Experiment 92. — Test for Sugar. 

Dissolve the soap in water, acidify with dilute sulphuric acid, 
filter off the precipitated fatty acids. Boil the filtrate for about 
half an hour, neutralize with sodium hydroxide, add a little of the 
neutralized solution to Fehling-Benedict solution, and boil for a 
minute. A red or yellow precipitate (cuprous oxide, Cu 2 0) shows 
sugar. 

Floating Soaps. — Floating soaps are made by beating the 
molten soap to incorporate air bubbles. 

Marine Soap. — Marine soap is a soap made from palm- 
nut or coconut oil, and takes its name from the fact that 
it will form a lather with sea water. Marine soap has 
been known to contain as much as 70 per cent of water. 

155 



156 ELEMENTARY HOUSEHOLD CHEMISTRY 

Mottled Soaps. — Soap with a faint gray mottle has been 
known for a very long time. The mottling was originally 
due to the use of rather impure fats and alkalies. When 
melted soap is solidifying, the more solid of its ingredients, 
sodium stearate and sodium palmitate, become solid before 
the sodium oleate. Some of the impurities, such as iron 
salts, tend to accumulate in the liquid sodium oleate. When 
the soap has all solidified, the dark-colored impurities are left 
in the places where the sodium oleate had accumulated. 
This gives a mottled appearance. 

Modern mottling, which is often much more pronounced 
than the older kind, is accomplished by the intentional addi- 
tion of coloring matters — ultramarine for blue, boneblack 
(carbon) or manganese dioxide for gray, etc. The mottling 
has no effect on the quality of the soap and has no bearing 
upon its real value. 

Medicated Soaps. — A great variety of medicinal substances 
are added to soaps. Carbolic acid, tar, and oatmeal are 
among the commoner ones. 

Soap Powders. — Soap powders are made by melting soda 
crystals (crystallized sodium carbonate) and adding soap. 
They may have as little as 1 or 2 per cent or as much as 20 
per cent of soap and from 10 to 60 per cent of water. 

Scouring Soaps. — Scouring soaps and scouring powders 
usually contain 10 to 20 per cent of soap, with 80 to 90 per 
cent of abrasive material — such as fine sand, ground pumice, 
whiting, or ground slate. Many also contain washing soda. 
The quality of such powders depends greatly on the fineness 
of the abrasive. Even a small proportion of coarse particles 
may do much damage by scratching. It is usually much 
more economical for the housekeeper to buy soap, soda, and 
abrasives, such as powdered bath brick, whiting, etc., separ- 
ately, and to mix them for immediate use. It is much easier 
to judge of the fineness of an abrasive separately than when 
it is mixed with soap. 



SPECIAL SOAPS AND SCOURING POWDERS 157 

Experiment 93. — Test for Soda or Pearl Ash and Coarse Abrasives. 

Apparatus : 
Bolting cloth sieves. 

Dissolve as much of the powdered material as possible in alcohol. 
Treat the residue with hot water. Filter. Acidify the filtrate. 
Effervescence shows the presence of water-soluble carbonates — 
sodium or potassium carbonate. 

Dry the residue from the treatment with water, and sift it suc- 
cessively through bolting cloths Nos. 4, 8, 12, and 16. The coarse 
particles of abrasive materials will be left on the sieves. By using 
a weighed quantity of soap (e.g. 100 grams) and weighing these 
coarse particles left on the sieves, we may estimate the proportion 
of coarse abrasive in the soap. 



CHAPTER XXX 

SOLUTION AND EMULSIFICATION OF FATS. THE 
CLEANING OF FABRICS 

Experiment 94. 

Materials : 

Cottonseed oil or olive oil, lard, and the liquids enumerated 
below. 
Caution. — Perform this experiment in a room in which no 
flames are burning. 

Put the oil into 8 test tubes, to the depth of § inch. Cover, 
respectively, to the depth of 1 inch, with the following liquids, 
shake, and allow to settle : (1) Ether, (2) Benzene (from coal tar), 

(3) Benzine (from petroleum. Note the difference in spelling), 

(4) Gasoline, (5) Kerosene, (6) Chloroform, (7) Carbon tetra- 
chloride, (8) Turpentine. 

- Put a little lard into a beaker or evaporating dish, add one of 
the more volatile of the above liquids, e.g. benzine or benzene, 
and stir for a minute or two. If the lard does not all dissolve, 
filter through a dry filter on to a watch glass, allow to evaporate 
in a warm place, and test the residue either by putting it in a cool 
place to see if it will solidify, or by stirring it with a little Sudan 
III solution, washing off with alcohol and adding hot water. (See 
Experiment 85, p. 149.) 

Experiment 95. 

Materials : 

Cottonseed or olive oil. 
Lard. 

Soap solution. 
Wood alcohol. 

Albumin solution (made either by mixing white of egg with 

an equal volume of water and beating with an egg beater, 

or by dissolving dry egg albumin in water). 

Put the oil into 7 test tubes to the depth of | inch. Cover with 

the following liquids to the depth of 1 inch, shake, and allow to 

settle : (1) Water, (2) Alcohol, (3) Wood alcohol, (4) Soap solu- 

158 



SOLUTION AND EMULSIFICATION OF FATS 159 

tion, (5) Sodium carbonate solution, (6) Albumin solution, 
(7) Albumin solution to which a few drops of sodium carbonate 
have been added. 

What general difference do you observe between the behavior 
of these liquids towards the oil and that of the liquids used in 
Experiment 94? What differences do you observe between the 
behavior of liquids 1, 2, and 3, and that of liquids 4, 5, and 7 of 
the present experiment? 

Shake lard with cold soap solution and with hot soap solution. 
In which instance does it behave like the oil? 

When a fat or oil dissolves in ether, gasoline, benzine (a 
petroleum product) or benzene (a coal-tar product), the 
product is a clear, homogeneous liquid, similar to that ob- 
tained by dissolving salt, sugar, or alcohol in water. This 
clear liquid is a solution. Liquid fats (oils) shaken with 
water, in which they are insoluble, break up into fine globules 
which are distributed through the water and impart to it a 
turbid appearance. This turbid suspension of oil in water 
rapidly separates into two clear layers, the lower one being 
water, the upper one oil. There are, however, certain sub- 
stances which when dissolved in water render it capable of 
holding the minute droplets of oil in more permanent sus- 
pension. Such a permanent or persistent suspension of oil 
in water is termed an emulsion. Soap is one of the best 
emulsifying agents. Washing soda and caustic soda have a 
similar effect — due to the formation of a certain amount of 
soap by their action upon the fatty acids always present in 
small quantities in natural oils. 

The detergent effect of soap is due to its emulsifying prop- 
erties. Those constituents of the dirt on soiled or spotted 
clothing which are not soluble in water are, as a rule, of a 
fatty nature. The addition of soap or soda to the water 
renders it capable of emulsifying the fats into fine droplets, 
which are then carried out of the fabric. The removal of 
the fat loosens any other dirt (earthy matter, etc.) which 
was held in position by the fat. 



160 ELEMENTARY HOUSEHOLD CHEMISTRY 

A number of plant and animal substances are known 
which have decided emulsifying power, and some of these 
have found use in household practice. Examples are ox 
gall {i.e. bile), soapbark, and soapwort. 

The Cleaning of Fabrics 

Stains on clothing commonly consist of a solid or sirupy 
substance holding miscellaneous particles of dirt. 

Numerous devices are used practically for the removal 
of such stains, but all of these are directed towards the re- 
moval of the dirt-retaining agent. If this is of the nature 
of a sugar, starch, or gum, hot water will remove the stain. 
Stains based on fats are, however, more troublesome. A fat 
may be removed: (i) By melting and absorption, (2) by 
solution, and (3) by emulsification. Blotting paper, Fuller's 
earth, French chalk, and pipe clay are among the best sub- 
stances used to absorb fats. A hot iron is used with the 
blotting paper or other absorbent to melt solid fats and to 
make liquid ones flow more readily. They flow away from 
the hot iron into the absorbent, which is placed beneath the 
cloth. 

Dry cleaning practice depends upon the solvent action of 
the liquids used. Of the solvents enumerated in the direc- 
tions for Experiment 94, only those can be used which evapo- 
rate quickly, so as to leave the cloth dry and free from dis- 
agreeable odor. Kerosene and turpentine are not sufficiently 
volatile for the purpose. Of the more volatile solvents, 
ether, benzene, benzine, and gasoline form explosive mix- 
tures with air, and are therefore not suitable for use in the 
same room with a stove, lamp, or flame of any kind. Ether 
and chloroform are objectionable on account of their anaes- 
thetic action. Carbon tetrachloride is the safest solvent 
to use, being non-inflammable and having only slight physio- 
logical effect. But the petroleum products, benzine and 



SOLUTION AND EMULSIFICATION OF FATS 161 

gasoline, are much cheaper, and are therefore frequently 
used. The disagreeable odor of benzine can be partially 
removed by shaking it with charcoal and then filtering — 
a process easily carried on in the household. A more effective 
method is to shake it with sodium plumbite (Na2Pb02) and 
redistill it. The odor is also sometimes masked by the addi- 
tion of oil of sassafras. 

Since grease spots frequently contain other substances 
than fats, a mixture of solvents may be more efficient than 
a single liquid. Mixtures of alcohol with one or more of the 
fat solvents are sometimes used, e.g. i drachm each of ether, 
chloroform, and alcohol are mixed with i quart of deodorized 
benzine. 

Common laundry practice is based largely upon the prin- 
ciple of emulsification, soap being the emulsifying agent. The 
use of hot water not only melts the fats, but assists the emulsi- 
fication. Sometimes the action of the soap is supplemented 
by that of a fat solvent, such as carbon tetrachloride, paraffin 
wax, kerosene, naphtha. (See Chapter XXVIII.) These 
liquids, although not miscible with water, are emulsified 
by the soap solution. A very good combination of emulsify- 
ing and solvent agents for fats is a mixture of carbon tetra- 
chloride with " Turkey-red oil." The latter is a substance, 
made by the action of sulphuric acid on castor oil, which 
dissolves in water, yielding a solution somewhat similar 
to that of soap. The mixture of Turkey-red oil and carbon 
tetrachloride is a clear liquid, which is readily miscible with 
water and which, like soap, renders the water capable of 
emulsifying fats. It may be used as a partial or total sub- 
stitute for soap in the laundry, and also for the removal of 
stains by the use of cold water. In cold water it is also excel- 
lent for the removal of grease from the hands. 



M 



CHAPTER XXXI 

THE GENERAL COMPOSITION OF FOODS 

Human foods — and the foods of animals in general — 
are complex mixtures of a large number of substances. The 
most important of these substances may be divided into two 
great classes, viz. : 

I. The Inorganic Foodstuffs. 

i. Water. 

2. " Mineral matter " or " ash." 
II. The Organic Foodstuffs. 

i. Fats. 

2. Carbohydrates. 

3. Proteins. 

,The organic foodstuffs are compounds which contain 
the element carbon ; the inorganic foodstuffs are those 
which do not contain carbon. The organic foodstuffs can 
be burned ; the inorganic are incombustible. 

The Inorganic Foodstuffs 

Water is not only taken as a separate article of diet, and 
as the chief constituent of all beverages, but is also present 
in great abundance in some classes of solid foods, especially 
in fresh fruits, fresh vegetables, and fresh meats. Even 
many foods which are apparently dry contain very material 
quantities of water. Wheat flour, for example, contains 
about 12 per cent of water, and bread about 35 per cent. 
The amount of water in a food is determined (i.e. measured) 
by weighing the food, heating it to the boiling point of water 
until it ceases to lose weight, and then weighing the dried 
residue. The loss in weight represents the water which has 
been driven off. The weight of the residue represents the 

162 



THE GENERAL COMPOSITION OF FOODS 163 

combined weight of the organic foodstuffs and the mineral 
matter. 

Experiment 96. 

Materials : 

Potato, turnip, or apple. 
Apparatus : 

Scales and weights. 
Water bath. 
Cut a slice of potato, turnip, or apple weighing about 25 grams. 
Immediately weigh it accurately. Cut up into fine, very thin 
pieces, place in a weighed dish, and dry on the water bath for 
several hours. Allow to cool in a dry atmosphere, and weigh the 
residue. Heat again on the water bath for an hour, allow to cool, 
and weigh. If the weight has not changed in the second weighing, 
the drying is completed. Deduct the weight of the dish, and cal- 
culate the percentage of moisture the vegetable or fruit contains. 

EXERCISE 

Consult the tables of food composition in Appendix A, and 
arrange the following foods in order of their water content, be- 

12. Walnuts 

13. Beef, hindquarter 

14. Salmon 

15. Whole milk 

16. Cream 

17. Butter 

18. White of eggs 

19. Yolk of eggs 

20. Oysters 

21. Apple pie 

22. Doughnuts 

When a food is thoroughly dried, the water all passes off 
as water vapor (steam). When the dried residue is strongly 
heated in the air, the organic foodstuffs are burned and pass 
off as gases and the inorganic salts remain behind in the ash. 
It must not be thought, however, that the ash consists en- 
tirely of salts which were present as such in the food. The 



ginning 


with the driest. 


1. 


Bananas 


2. 


Apples 


3- 


Grapes 


4. 


Watermelons 


5- 


Green cucumbers 


6. 


Tomatoes 


7- 


Potatoes 


8. 


Cabbage 


9- 


Oatmeal 


10. 


Flour 


11. 


Bread 



1 64 ELEMENTARY HOUSEHOLD CHEMISTRY 

sulphur, phosphorus, and chlorine, and the potassium, so- 
dium, calcium, and magnesium, which exist in the ash as 
sulphates, phosphates, and chlorides, may have been con- 
stituents of organic compounds in the unburned material. 
And the carbon which exists in the ash as a constituent of 
carbonates must have come either from the salts of organic 
acids or from more complex organic compounds, such as 
fats, carbohydrates, and proteins. 

Nevertheless,' the weight of the ash is regarded as a rough 
measure of the quantity of mineral matter in the food. 
The ash contains all the potassium, sodium, calcium, and 
magnesium and iron of the food. Part of the chlorine, sul- 
phur, and phosphorus, however, may pass off as gases during 
the combustion of the food. 

Except in foods which have been salted, the ash seldom 
amounts to five per cent of the weight of the food. In many 
foods it amounts to less than one per cent. 

The Organic Foodstuffs 

The nature of fats has already been discussed in connection 
with the manufacture of soaps and the removal of dirt from 
fabrics (Chapters XXV, XXVI, and XXX). Sugar and 
starch are typical carbohydrates. The white of egg, the 
lean of meat (muscle fibers), and the gluten of flour are ex- 
amples of proteins. 

It should be noted that while both fats and carbohydrates 
are composed of carbon, hydrogen, and oxygen, the propor- 
tion of carbon is much greater, and the proportion of oxygen 
much smaller in the former class of substances than in the 
latter. 

Proteins differ from fats and carbohydrates in containing 
a fairly large proportion of nitrogen and a small proportion 
of sulphur, in addition to carbon, hydrogen, and oxygen. 
Besides these five elements a number of proteins contain a 



THE GENERAL COMPOSITION OF FOODS 



I<55 



small proportion of phosphorus. A few also contain iron 
or other elements. 

The average composition of the three great classes of or- 
ganic nutrients is given in the following table : 

AVERAGE ELEMENTARY COMPOSITION OF NUTRIENTS 





Fats 


Carbohydrates 


Proteins 




Per Cent 


Per Cent 


Per Cent 




76.5 


44.4 


53 


Hydrogen 


I2.0 


6.2 


7 


Oxygen 


ii-5 


49.4 


2 3 


Nitrogen 


— 


— 


16 


Sulphur ....... 


— 


— 


1 



The percentage of hydrogen in proteins does not differ 
greatly from that in carbohydrates. In carbon and in 
oxygen content, the proteins are intermediate between the 
fats and the carbohydrates. 



CHAPTER XXXII 

THE CARBOHYDRATES. I 

Before taking up the consideration of the functions of the 
various classes of foodstuffs it is desirable that we should 
learn something about the chemical constitution and be- 
havior of the carbohydrates and proteins, similar to what 
we have already learned about the fats. 

Carbohydrates (literally, hydrates of carbon) take their 
class name from the circumstance that in combination with 
carbon they contain the elements of water in the same pro- 
portion as water itself. Examples are glucose, C 6 Hi 2 6 ; 
cane sugar, C12H22O11 ; starch, (C 6 Hi O5) n . But the name 
does not adequately describe the class ; for, on the one hand, 
many compounds which are not carbohydrates {e.g. form- 
aldehyde, CH 2 ; acetic acid, C2H4O2 ; lactic acid, C3H6O3) 
contain hydrogen and oxygen in this proportion combined 
with carbon ; and on the other hand there are a few rare 
carbohydrates whose molecules have more than twice as 
many hydrogen atoms as oxygen atoms. 

The simplest carbohydrates are called monosaccharides. 
These are sweet-tasting substances, which are so abundantly 
soluble in water as to form sirups with it. In short, they 
are sugars. Honey is a sirup of two monosaccharides, called 
glucose (or dextrose) and fructose (or levulose) , together with 
a small proportion (less than 10 per cent) of that sugar 
(cane sugar) which is most familiar to us — and which is not 
a monosaccharide. (See beyond.) 

Now, the term carbohydrates embraces the monosac- 
charides and all substances which by hydrolysis are converted 
into monosaccharides. 

Monosaccharides are divided into two classes — aldoses and 
ketoses — according to their structural formulas, and into several 

166 



THE CARBOHYDRATES 167 

classes — pentoses, hexoses, etc. — according to the number of 
carbon atoms they contain. Glucose and fructose are both 
hexoses, having the molecular formula, C 6 H 12 6 . Structurally, 
glucose is an aldose, fructose a ketose. Aldoses contain the radicle 
or " group " of atoms : 

— C=0 

which is common to a class of compounds called aldehydes, of 
which the disinfectant, formaldehyde, 

/ H 
H— C=0 

and the flavoring matter, benzaldehyde (oil of bitter almonds), 

C 6 H 5 — C=0 
are familiar examples. 

Ketoses contain the group =C=0, joined to two other car- 
bon atoms, and belong to a class of compounds called ketones. 
Acetone, 

CH 3 v 

>c=o, 

CH 3 X 

a product of the dry distillation of wood, is the simplest represent- 
ative of the ketones. 

The structural formulas of glucose and fructose are : 





H 

1 


H 

1 


H- 


-C— OH 


H— C— OH 

1 


H- 


-C— OH 

1 


H— C— OH 


H- 


-C— OH 


H— C— OH 


HO- 


-C— H 


HO— C— H 


H- 

hicose 


-C— OH 

l/H 

^0 

: (Dextrose) 


C=0 

H— C— OH 

1 
H 

Fructose (Levulose) 



1 68 ELEMENTARY HOUSEHOLD CHEMISTRY 

It is clear from these formulas that these monosaccharides, 
in addition to being aldehydes or ketones, are also alcohols 
containing several — OH groups. And this alcoholic con- 
stitution appears to be true of all the carbohydrates, however 
complex their molecules. 

Carbohydrates may be classified as follows : 

I. Sugars. — These form crystals and dissolve in water. 
In solution they will pass through membranes of parchment 
paper. They have a sweet taste. 

The most important sugars are : 

(i) The monosaccharides — glucose, fructose and galac- 
tose. 
(2) The disaccharides — maltose, lactose, and sucrose. 

II. Polysaccharides. — This class includes dextrin and 
some other gums, pectin, starch, glycogen, and cellulose. Dex- 
trin, pectin, and glycogen are soluble in water, but do not 
pass through parchment paper with the water. Starch is 
insoluble in cold water and cellulose insoluble even in hot 
water. 

Experiment 97. 

Materials : 

Monosaccharides : 

Glucose (dextrose, grape sugar). 
Fructose (levulose, fruit sugar). 
Disaccharides : 

Maltose (malt sugar). 
Lactose (milk sugar). 
Sucrose (saccharose, cane sugar). 
Polysaccharides : 
Dextrin. 
Starch. 

Cellulose (absorbent cotton or filter paper). 
Taste the carbohydrates. The sweet ones are sugars. Which 
of the above classes are included under this term? 

Test the solubility of the carbohydrates in cold water by shak- 
ing about ^ gram of each with half a test tube of water. Which 
of them are insoluble in cold water? Which one of the sugars is 



THE CARBOHYDRATES 169 

much less soluble than the others? How does this one compare 
with the others in sweetness? Keep the solutions for subsequent 
experiments. 

Find out whether any of the carbohydrates insoluble in cold 
water is soluble in hot water. Keep the solutions. 

Experiment 98. — Fehling's Solution, Fehling-Benedict Solution, 
and the Meaning of " Reduction." 

Materials : 

Cuprous oxide, Cu 2 0, and Cupric oxide, CuO. 
Solutions of : 

Copper sulphate, 17.3 grams to 1 liter. 
Sodium potassium tartrate (Rochelle salt), 346 grams to 
1 liter. 
Sodium citrate, 173 grams to 1 liter. 

(a) Note the colors of the two oxides of copper. Which of the 
two contains the larger proportion of oxygen? (See p. 39.) 

To " reduce " a compound is to take away oxygen from it. 
Which of the oxides of copper can be changed into the other by 
reduction ? 

(b) Dissolve a little of the cupric oxide in dilute sulphuric acid. 
What salt is present in the solution so prepared ? Write equation 
for its formation. We may regard this salt as containing cupric 
oxide, CuO, combined with SO3, the anhydride of sulphuric acid. 

Acid anhydrides are the oxides which bear to acids the same 
relation that the basic oxides bear to the bases ; i.e. : 

Anhydride -f- Water = Acid 

Thus, carbon dioxide, C0 2 , is the anhydride of carbonic acid, 
H 2 C0 3 ; sulphur dioxide, S0 2 , the anhydride of sulphurous acid, 
H0SO3, etc. 

(c) Add to a little of the solution prepared in (b) a little more 
than enough sodium hydroxide solution to neutralize the acid. 
What is the precipitate? Add more sodium hydroxide and boil. 
What is formed ? (Compare Expt. 49.) 

(d) To copper sulphate solution add, first, Rochelle salt solu- 
tion, and then sodium hydroxide. What effect has the Rochelle 
salt on the reaction between sodium hydroxide and copper sul- 
phate ? We may regard the resulting solution (Fehling's solution) 
as containing cupric oxide, CuO. 

(e) Make the same experiment as (d), using sodium citrate in- 
stead of Rochelle salt. 



170 ELEMENTARY HOUSEHOLD CHEMISTRY 

(/) To copper sulphate solution add sodium carbonate solution. 
What is the precipitate ? Can it be regarded as containing cupric 
oxide ? 

(g) To copper sulphate solution add, first, sodium citrate, then 
sodium carbonate. The product is Fehling-Benedict solution, 
which keeps better than Fehling's solution. Can Fehling-Benedict 
solution also be regarded as containing cupric oxide? 

When Fehling's or Fehling-Benedict solution is reduced, 
cuprous oxide is formed. This oxide is not capable of forming 
soluble compounds with tartrates and citrates similar to those 
formed by cupric oxide, and is therefore precipitated. The 
precipitate obtained is, however, not always red, but often, 
especially with the Fehling-Benedict reagent, yellow or green, 
probably due to the presence of more or less cuprous hydroxide. 

Experiment 99. 

Materials : 

The solutions of sugars prepared in Experiment 97. 

, To separate 5 cc. portions of Fehling-Benedict solution add a 

few drops of the sugar solutions. Boil for a minute or two. What 

is the precipitate? Which of the sugars produce it? These are 

called " reducing sugars." What sugar is not a reducing sugar? 

Experiment 100. 

Materials : 

Sucrose solution prepared in Experiment 97. 

To the sucrose solution add a little concentrated hydrochloric 
acid. Boil for a minute or two. Cool. Put in a small piece of 
litmus paper and add sodium hydroxide little by little until the 
acid is neutralized. Add a little of the neutralized solution to 
about 5 cc. Fehling-Benedict solution, and boil. 

Does unchanged sucrose affect Fehling-Benedict solution? 
What change must have been caused by boiling the sucrose with 
the hydrochloric acid? 

Experiment 101. 

Material : 
Starch. 

Absorbent cotton (cellulose). 
Sodium carbonate powdered (soda ash). 



THE CARBOHYDRATES 171 

(a) In a beaker or dish mix a little starch (| to ^ gram) with a 
teaspoonful of water. Heat about 50 cc. of water in a dish to 
boiling, and add the mixture of starch and cold water. Boil for 
a minute or two, stirring constantly. 

(b) Pour off some of the solution into a test tube and cool it 
under the tap. To a small portion of the cold solution add a little 
iodine solution. Warm the solution and cool it again. Does 
iodine color hot starch solution? 

(c) To another portion of the cold solution add a few drops of 
concentrated sulphuric acid. Boil until a drop of the liquid 
poured off into cold iodine solution no longer colors the latter. 
This is evidence that starch is no longer present. Pour off the 
main portion of the boiled solution into a beaker and add powdered 
sodium carbonate, little by little, until the acid is neutralized. 
Add a little of this neutralized solution to Fehling-Benedict solu- 
tion in a test tube, and boil for a minute. 

What do you infer as to the effect of boiling the starch with the 
acid? 

(d) Put a little absorbent cotton into a test tube, cover it with 
concentrated sulphuric acid, and allow to stand a minute or two. 
Note whether the cellulose dissolves in the sulphuric acid. Pour 
off into five or six times its volume of cold water and boil for two or 
three minutes. Neutralize the acid (in a beaker) with sodium 
carbonate as in (c), add to Fehling-Benedict solution, and boil. 

It is evident from the above experiments that reducing 
sugars can be formed from cane sugar, starch, and cellulose 
by boiling with acids. The acid is, however, not used up in 
the reaction, which is really one between the carbohydrates 
and water — in other words, a hydrolysis. The acid is merely 
a catalytic agent, promoting the hydrolysis. 

The final products of hydrolysis of all the higher carbohy- 
drates (disaccharides and polysaccharides) are monosac- 
charides. Each disaccharide molecule hydrolyzes into two 
monosaccharide molecules, and each polysaccharide molecule 
into several monosaccharide molecules. The relations of the 
more familiar higher carbohydrates to the monosaccharides 
are as follows : 



172 ELEMENTARY HOUSEHOLD CHEMISTRY 

1. Disaccharides: 

Sucrose + Water = Glucose + Fructose 
Lactose + Water = Glucose + Galactose 
Maltose + Water = Glucbse + Glucose 

All three of these reactions are expressed by the equation : 
C12H22O11 + H2O = C6H12O6 -+- CeH^Oe 

2. Polysaccharides : 

Dextrin + Water = Glucose 
Starch + Water = Glucose 
Glycogen + Water = Glucose 
Cellulose + Water = Glucose 

All of these reactions correspond to the equation : 
(C 6 H 10 O 5 )„ + n H 2 = n C 6 H 12 6 

in which n stands for an unknown number. 



CHAPTER XXXIII 

THE CARBOHYDRATES. II 

Description of the Monosaccharides, C 6 Hi 2 6 

Glucose, also called dextrose and grape sugar, occurs very 
widely distributed in plant juices, and also in smaller pro- 
portions in the blood of animals. It is a prominent constitu- 
ent of honey and of raisins, and sometimes separates from 
these in the solid form. It does not crystallize nearly as 
readily as sucrose (cane sugar), however, and in the processes 
used to separate the latter from the juice of the sugar cane and 
from the juice of the sugar beet, the glucose remains in the 
molasses. It is less sweet than sucrose. 

Commercial glucose, which appears on the market both 
in solid form and in a sirup, is manufactured by hydrolysis 
of starch by an acid. In addition to glucose proper, com- 
mercial glucose contains the polysaccharide dextrin, and the 
disaccharide maltose, — these being also formed by the hy- 
drolysis of starch. Commercial glucose is cheaper than cane 
sugar, and is sometimes used as a substitute for, or as an 
adulterant of, the latter. It is also " compounded " {i.e. 
mixed) with cane sirup to form a table sirup known as 
" corn sirup." 

Fructose, also called levulose (or laevulose) and fruit 
sugar, is found associated with glucose in fruit juices and in 
honey. A mixture of equal quantities of glucose and fruc- 
tose is produced when cane sugar is hydrolyzed. 

In the preparation of jams and preserves much of the 
cane sugar put in is hydrolyzed by the acids of the fruit, 
and the jam and preserves contain this mixture of glucose 

173 



174 ELEMENTARY HOUSEHOLD CHEMISTRY 

and fructose. The hydrolysis of sucrose is technically spoken 
of as the inversion of sugar, and the mixture of equal quanti- 
ties of glucose and fructose as invert sugar. 

The term " inversion " refers to an effect which sugar solutions 
have upon so-called " plane-polarized " light. In terms of the 
wave theory of light, plane-polarized light has all its vibrations in 
one plane at right angles to the direction of the ray, while ordinary 
light has vibrations in all directions at right angles to the direction 
of the ray. The instrument used to measure the effect of sub- 
stances upon polarized light is called a polariscope or polarim- 
eter. It consists essentially of two prisms of calcite (crystallized 
calcium carbonate) at opposite ends of a tube. One prism is 
fixed in position ; the other can be rotated about the axis of 
the tube. When light admitted through the fixed prism is al- 
lowed to pass through air or water to the second prism, it only 
passes completely in case this second prism is in a similar posi- 
tion to the first. If the second is rotated into a position at 
right angles to the first, the light is shut out entirely. In inter- 
mediate positions it is partially transmitted. Now, if in passing 
from prism to prism the light passes through a sugar solution, 
the second prism being in a similar position to the first, the light 
is no longer fully transmitted through the second prism. If, 
however, this second prism be rotated — it may be to the right 
or it may be to the left — through a certain angle, the light will 
be fully transmitted. The angle through which the prism has 
to be rotated is equal to the angle through which the " plane of 
polarization " is rotated by the sugar solution. 

Now, sucrose and glucose rotate the plane of polarization to 
the right, while fructose (" levulose ") rotates it to the left. At 
room temperature fructose rotates the plane more to the left 
than an equal quantity of glucose rotates it to the right. Hence, 
invert sugar is levorotatory, 1 and the hydrolysis of the sucrose 
changes a dextrorotatory solution into a levorotatory one. 

Galactose does not occur as such, but is produced by 
hydrolysis of lactose and of certain higher carbohydrates, 
galactans, which bear to it a similar relation to that which 
starch bears to glucose. 

1 Latin, Icbvus = left, dexter = right. 



THE CARBOHYDRATES 175 

Alcoholic Fermentation 

The ferment, zymase, contained in yeast, causes the mono- 
saccharides to decompose into alcohol and carbon dioxide : 

C 6 H 12 6 = 2 C2H5OH + 2 C0 2 

This is the reaction which characterizes the fermentation of 
fruit juices. It is made use of in the manufacture of wines 
and sometimes occurs in jars of fruit which have not been 
thoroughly sterilized. The same reaction is involved in the 
final stage of fermentation of grains in the manufacture of 
beer and whisky, and in the raising of bread. 

Description of the Disaccharides, C12H22O11 

Sucrose, also called saccharose and cane sugar, is of very 
common occurrence in the vegetable world, being found in 
considerable quantity in the fruits and juices of many plants 
— usually mixed with more or less glucose and fructose. 
The most important sources of sucrose are the sugar beet, 
sugar cane, sorghum cane, and sugar maple. 

Pure sucrose obtained from any of these sources does not 
differ from that obtained from any of the others. Rock 
candy is chemically pure sucrose, and commercial white 
sugar contains very little impurity. 

The hydrolysis (inversion) of cane sugar can be brought 
about by boiling the aqueous solution with an acid. Hence 
this reaction takes place in the preserving of fruits. (See 
above.) It can also be accomplished by one or more fer- 
ments commonly called invertases or invertins, but more 
correctly termed sucrases. There is a ferment of this class 
in the yeast plant (which assists in alcoholic fermentation by 
converting sucrose into glucose and fructose) and another 
in the intestinal juice (which effects the same change as a 
step in the digestion of sugar). 



176 ELEMENTARY HOUSEHOLD CHEMISTRY 

Experiment 102. 

Materials : 

Yeast. 

Cane sugar. 

Sand. 

Mortar and pestle. 
Grind a yeast cake with sand and a little water. Dilute to 50 cc., 
add 5 cc. ether, and filter. To the nitrate add 100 cc. alcohol. 
This precipitates the sucrase (invertase). Filter. Change the 
receiver and dissolve the precipitate by pouring about 20 cc. water 
through the filter. 

Dissolve about \ gram sugar in a half test tube of water. Add 
a little of the sucrase solution just prepared, and allow to stand 
about half an hour. Then add a little of the solution to Fehling- 
Benedict solution, and boil for a minute or two. If no precipitate 
is formed, allow the sugar solution to stand another half hour and 
repeat the test. 

Cane sugar has no action on Fehling's solution, but invert 
sugar, of course, has. In other words, cane sugar is non- 
reducing, but yields reducing sugars upon hydrolysis. 

Maltose, or malt sugar, yields only a single kind of monosac- 
charide — one molecule of maltose hydrolyzing to two mole- 
cules of glucose. This hydrolysis is readily effected by boiling 
the maltose with dilute strong acids. It is also brought 
about by the action of ferments, called maltases, one of which 
is a constituent of the intestinal juice. Maltose is formed 
from starch by the action of amylolytic {i.e. starch-hydro- 
lyzing) ferments, amylases. An amylase known as diastase 
is developed in germinating grain and hence is present in 
malt, malt extract, and beerwort. Two amylases are con- 
cerned in digestion of starch. These are the ptyalin of the 
saliva and the amylopsin of the pancreatic juice. Maltose 
is also formed as an intermediate product when starch is 
hydrolyzed by boiling with acid, as in the manufacture of 
commercial glucose. 

Lactose — milk sugar or sugar of milk — hydrolyzes to 
glucose and galactose. It occurs in the milk of mammals. 



THE CARBOHYDRATES 177 

Fresh cow's milk contains about five per cent. Lactose 
is much less soluble in water than the other sugars, and 
has only a slightly sweet taste. It is commonly used in 
pharmacy as a " base " (or diluent) for pills and tablets. 
In digestion lactose is hydrolyzed in the intestine under the 
influence of a ferment known as lactase. Lactose is con- 
verted into lactic acid by a certain class of bacteria which are 
normally present in fresh milk and are very abundant in 
buttermilk. The souring of milk is due to this fermentation. 
Maltose and lactose reduce Fehling's solution. 

The Polysaccharides (CeH^Os)^ 

Starch is the principal form of digestible carbohydrate 
in cereal grains and their products and in potatoes. It 
constitutes more than half the solid matter of all the common 
cereals and about three fourths of that of the potato. Being 
the principal storage form of carbohydrates in most green 
plants, starch is found in more or less abundance in almost 
all vegetable foods. For commercial purposes starch is 
isolated from wheat, maize (corn), rice, and potatoes. Arrow- 
root, tapioca, and sago are also almost pure starch. All these 
commercial forms of starch contain water, about eighteen 
per cent as an average. Starch granules of different plants 
vary in size and structure ; so the source of a starch which has 
not been altered by heat, fermentation, or the action of chemi- 
cal reagents can be determined by microscopic examination. 

Experiment 103. 

Materials : 
Cornstarch. 
Potato starch. 
Wheat starch. 
Apparatus : 

Compound microscope. 
Slides. 

Cover glasses. 
Medicine dropper. 

N 



178 ELEMENTARY HOUSEHOLD CHEMISTRY 

Prepare the three starches for microscopic examination by first 
sifting through a 60- or 80-mesh sieve, then placing a small portion 
on a slide by means of a knife point, adding a drop of distilled 
water, putting on the cover glass obliquely (so as to avoid in- 
closing air bubbles) and then rubbing out the material under the 
cover glass between the thumb and finger to separate the particles 
and distribute them evenly. 

Examine the starches under the microscope, using a magnifica- 
tion of about 250. Note the general form and comparative size 
of the granules, and the presence or absence of concentric ring 
markings and of the little depression called the hilum. 

The granules of these three starches are typical of the three 
general forms — the circular, the irregularly oval, and the polygonal. 
Note, however, that wheat starch consists of two kinds of granules 
— the larger having one form, the smaller another. In the form 
of their granules rye and barley starches resemble wheat starch; 
arrowroot, pea, and bean starches resemble potato ; and oats, 
buckwheat, and rice resemble corn. 

The most characteristic chemical test for starch is the re- 
action with iodine in the cold. (See Expt. 101 (b) above.) 

When starch is treated with hot water, the granules swell 
and burst, and the starch apparently dissolves in the water, 
forming an opalescent liquid or paste. In many respects 
this liquid differs from the solutions of such substances as 
salts, acids, bases, and sugars. These latter substances, 
which separate from their solutions in crystalline form, are 
known as crystalloids, while starch is a colloid (literally, glue- 
like substance). When a starch solution evaporates, no 
crystals form, but the starch gradually dries to a hard, horn- 
like or glue-like mass, from which it is very difficult to drive 
off the last traces of water. An important difference between 
colloids and crystalloids in solution will be referred to later. 
(Chapter XXXVII.) 

The hydrolysis of starch by acids and by amylases has 
been referred to in connection with glucose and maltose. 
On standing in the cold with a dilute strong acid, starch is 
converted into a soluble substance which gives a blue color 



THE CARBOHYDRATES 1 79 

with iodine, and does not reduce Fehling's solution. This 
is known as soluble starch. Similar products are formed by 
the action of organic acids, dilute alkalies, and other reagents. 

Further hydrolysis (by longer standing or by heating with 
acid) produces soluble substances known as dextrins, some 
of which give a red coloration with iodine, while others give no 
coloration at all. Commercial dextrin is prepared by heating 
starch for some time to about 200 C. about (400 F.) or by 
moistening with dilute nitric or hydrochloric acid and heat- 
ing to a lower temperature (100-120 C). In breadmaking 
some dextrin (together with maltose) is formed during the 
rising by the action of diastase on the starch of the flour. 
In the baking a further portion of the starch in the crust is 
converted into dextrin by the heat. The effect of toasting 
bread is to convert some of its starch into dextrin. It is 
present in considerable abundance in some of the malted 
breakfast foods. 

Dextrin is white when pure, but commonly yellow in com- 
mercial samples. It is soluble in water, giving a strongly 
dextrorotatory solution (whence the name). The solution 
is colloidal, and on drying behaves like that of a starch. Dex- 
trin is used as a substitute for natural gums (some of which 
are analogous carbohydrates) in the manufacture of mucilage, 
label gums, and " sizes " for giving a glazed finish to textiles, 
cardboard, and paper. Dextrin is precipitated from its 
aqueous solution by the addition of alcohol. 

Glycogen, sometimes called animal starch, is similar to 
dextrin in properties. It plays a part in animal organisms 
similar to that played by starch in the vegetable world, — 
the part of a " reserve "or " storage " carbohydrate. It 
is found in the muscles and more abundantly in the liver, the 
amount present varying greatly with the condition of nutri- 
tion of the animal. Stored glycogen is rapidly used up under 
conditions of starvation and of hard muscular work. Gly- 
cogen is a white powder, soluble in water to an opalescent 



180 ELEMENTARY HOUSEHOLD CHEMISTRY 

colloidal solution. With iodine it gives a reddish coloration, 
somewhat similar to that given by dextrin. 

The celluloses constitute the walls of the cells of plants, 
thus acting as a sort of plant skeleton. Celluloses are in- 
soluble in water and in dilute acids and alkalies. The " crude 
fiber " which the analyst determines in foods, by successively 
treating with dilute acid and alkali, and weighing the un- 
dissolved residue, consists mainly of cellulose. By heating 
with strong acid, ordinary cellulose — such as that of cotton 
and linen — is hydrolyzed, yielding glucose. Cotton and 
linen are comparatively pure cellulose, and straw, wood, and 
paper contain large proportions of this class of carbohydrates. 

The proportion of cellulose in different parts of a plant 
vary widely. It is usually most abundant in the stem, with 
less in the foliage and least in the fruit. Such vegetables 
as celery, beets, and turnips contain much more cellulose than 
do potatoes, flour, and fruits. As a plant matures, its cell 
walls thicken. Consequently the proportion of cellulose 
in its stem, branches, and roots increases, and some of the 
cellulose is converted into a harder form called lignocellulose 
or woody tissue. This accounts for the toughness of over- 
mature vegetables. 

Cellulose is digested to only a slight extent. The foods 
rich in cellulose, e.g. turnips and green vegetables, do not 
contribute much to the fuel value of the diet. As regulators 
of physiological processes, however, they are of importance, 
both on account of the salts and other ash constituents which 
they contain and on account of the cellulose which mechani- 
cally stimulates the intestines, inducing peristaltic action. 

Pectin is a polysaccharide contained in the juices of some 
fruits, e.g. red currants, and obtained from the pulp of many 
fruits and vegetables, and from the inner peel of oranges 
and lemons upon boiling with water. The addition of alcohol 
to such juices or extracts precipitates the pectin as a jelly. 
If the solutions are rich enough in pectin, or if they are boiled 



THE CARBOHYDRATES 181 

down until they are rich enough in pectin, either an acid or a 
sugar will also precipitate the pectin. In the making of 
fruit jellies and marmalades the acid naturally present in the 
fruit juices and the added sugar serve to precipitate the 
pectin, and the secret of successful jelly making is to have 
the proportions of pectin, water, acid, and sugar so adjusted 
that the pectin is precipitated as a continuous network, 
filling the whole mold or glass into which it is poured. By 
boiling with strong acid, pectin can be hydrolyzed to reduc- 
ing sugars, but the products obtained are probably not 
identical with any of the familiar sugars described above. 

Caramel. — When cane sugar is heated, it melts at about 
160 C. (320 F.), and at a little higher temperature begins to 
decompose. Effervescence occurs due to the evolution of 
water, and the melted sugar acquires a dark color and a 
peculiar flavor. Sugar which has suffered this change is said 
to be caramelized, the color and flavor being attributed to 
caramel (from the Latin, calamellus, sugar cane). In addition 
to caramel the caramelized sugar may contain glucose. When 
caramelized sugar is dissolved in water and fermented with 
yeast, the glucose and unchanged sucrose are destroyed and 
the caramel is left unaffected. Caramel has a dark brown 
color and a bitter taste. It is sometimes used to color milk 
and cream. Caramel is not a single substance, but a mixture 
of several compounds, all of which differ from cane sugar in 
that they reduce Fehling's solution and are not fermented 
by yeasts. Glucose, melted and heated, also loses water and 
yields caramel, and lactose yields a similar product known as 
lacto-caramel. The color and flavor of taffy are due to cara- 
mel, and it is produced in many cooking operations. Sugar 
which has been melted and only slightly yellowed by heating 
to 160 C. (320 F.), as in making taffy, is called barley 
sugar. 



CHAPTER XXXIV 

THE PROTEINS. I 

The most important plant and animal substances contain- 
ing the element nitrogen are the proteins. Being indispensa- 
ble constituents of the cells of which all vegetable and animal 
organisms are made up, proteins are essential to life. Other 
nitrogen compounds than proteins exist in plants and ani- 
mals. Among such are ammonium salts ; the alkaloids, such 
as the caffein of tea and coffee, the nicotine of tobacco, and 
the quinine of Peruvian bark ; the amides, such as asparagine 
and urea; the extractives of meat, such as creatine and 
creatinine. 

These substances are chemically simpler than the proteins ; 
in other words, they are made up of smaller molecules. 
But their relative abundance is so small that when a chemist 
wishes to estimate the quantity of protein in a food, he com- 
monly ignores the presence of these simpler nitrogenous 
compounds and calculates the quantity of protein by mul- 
tiplying the total quantity of nitrogen found by 6.25. 

The reason for using this factor is that, on the average, 
proteins contain 16 per cent of nitrogen, and 16 X 6.25 = 100. 

It will be realized that this is only a rough way of deter- 
mining the quantity of protein in a food, but it is the method 
almost universally used. 

The proteins resemble the polysaccharides in having very 
complex molecules, in forming colloidal solutions, and in 
being hydrolyzable into crystalloid substances. The crystal- 
loid substances into which the proteins are ultimately con- 
verted by hydrolysis are the so-called amino acids. 

182 



THE PROTEINS 183 

An amine is a compound constituted like ammonia but having 
in place of one (or more) of the hydrogen atoms of the ammonia 
molecule an organic radicle attached to the nitrogen atom. Thus : 

/ H / H / H / H 

N^-H N^H N^-H Nf-H 

\h \ch 3 \c 2 h 5 \c 6 h 5 

Ammonia Methylamine Ethylamine Phenylamine 

(Aniline) 

An amino acid is a compound which is at the same time an 
amine and an acid. Its molecule, therefore, contains both the 
amino, — NH 2 , and the carboxyl, — COOH, groups. The simplest 
substances of the class are glycine and alanine, which have the 
structural formulas : 

CH 3 
CH 2 NH 2 I 

I CH NH 2 

COOH I 

COOH 
Glycine Alanine 

Two or more amino-acid molecules can be converted into a 
peptide and water thus : 

2 NH 2 . CH 2 . COOH = NH 2 . CH 2 . CO . NH . CH 2 . COOH + H 2 

Glycine Glycyl glycine, a dipeptide 

NH 2 . CH 2 . COOH + CH 3 . CH NH 2 . COOH= 

CH 3 . CH NH 2 . CO . NH . CH 2 . COOH 

Alanyl glycine, a dipeptide 

2 NH 2 . CH 2 . COOH + CH 3 . CH NH 2 . COOH = 

CH 3 . CH NH 2 . CO . NH . CH 2 . CO . NH . CH 2 . COOH + 2 H 2 0. 

Alanyl glycyl glycine, a tripeptide 

Upon hydrolysis these reactions are reversed, the peptides being 
resolved into amino acids. Now, it is probable that the proteins 
of plants and animals are peptides made up of a great many amino- 
acid molecules, joined together in the way indicated above. 
Peptides made up of a large number of amino-acid molecules are 
designated polypeptides. The proteins, therefore, are regarded as 
polypeptides. 



1 84 ELEMENTARY HOUSEHOLD CHEMISTRY 

In all, about twenty amino acids have been obtained from the 
various proteins by hydrolysis, and a single protein may yield 
all of them, and usually does yield the greater number of them. 
Some of these twenty-odd amino acids contain more than 
one amino group, some more than one carboxyl group, some 
contain sulphur, and there are various other complications. 

The proportions of the various amino acids yielded by the 
various proteins differ widely. For instance, comparing the 
following proteins — casein from milk, gelatin prepared from 
the tendons of beef, gliadin from wheat, and zein from corn — 
we find that no glycine is yielded by casein, gliadin, or zein, 
while the amount yielded by gelatin amounts to one sixth of 
the weight of the gelatin. Again, while gelatin yields only 0.6 
per cent of alanine, casein yields 1.5, gliadin 2, and zein nearly 
10 per cent of this amino acid. Once more, tryptophane, one 
of the very complex amino acids, is not found among the 
hydrolysis products of gelatin or of zein, but gliadin yields 
-I per cent and casein ij per cent of this substance. 

In addition to amino acids, ammonia is formed in the 
hydrolysis of proteins, and from certain classes of proteins — 
the so-called " conjugated " proteins — still other products 
are obtained. Thus, hemoglobin, the red coloring matter of 
the blood, yields a pigment containing iron ; casein (the 
curd of milk) and vitellin of egg yolk yield phosphorus com- 
pounds ; the mucins yield carbohydrates ; and nucleins yield 
nucleic acid, a complex organic acid containing phosphorus. 
The amino acids and the other groups which enter into the 
molecules of the more complex proteins are often referred to 
figuratively as the " building stones " of the protein mole- 
cules. " Native " proteins {i.e. such as exist in plant and 
animal tissues and fluids) may be divided into two classes : 

1. Simple proteins, which yield no hydrolysis products 
other than amino acids and ammonia. 

2. Conjugated proteins, which yield other hydrolysis 
products in addition to amino acids and ammonia. 




Emil Fischer. — 1852-. 

A distinguished German chemist, whose researches upon the chemistry of 
the carbohydrates and proteins have contributed much to our knowledge of 
both these classes of compounds. 



THE PROTEINS 1 85 

Just as in the hydrolysis of starch, intermediate products 
— soluble starch, dextrins, maltose — between the starch 
and its ultimate product, glucose, were obtained, so also in 
the hydrolytic cleavage of proteins, intermediate products 
are obtained. Some of these products have still the essential 
characteristics of proteins. When egg-white is heated above 
73 C. (160 F.), for example, it hardens or " coagulates." 
It is thus converted from a substance soluble in water into 
one which is insoluble but is still essentially a protein. It is 
believed that this change is due to slight hydrolysis or hydra- 
tion of the protein molecule. Similarly, the soluble caseinogen 
of milk is readily converted into the insoluble protein, casein, 
by the action of the ferment rennin ; and the soluble fibrino- 
gen of the blood clots into fibrin when the blood is exposed 
to air. Such slightly altered proteins are called " derived 
proteins " or protein derivatives. Another class of derived 
proteins are obtained by further hydrolysis of such primary 
derivatives as coagulated egg albumin, fibrin, and casein. 
Such hydrolysis can be accomplished by the action of diges- 
tive ferments (such as the pepsin found in the stomach and 
the trypsin found in the small intestines) and the products 
are substances soluble in water and not coagulated by heat. 
The substances so produced are called proteoses and peptones. 
Proteoses are more complex and less soluble in salt solutions 
than peptones, but no very sharp line of distinction can be 
drawn between the two classes of compounds. The term 
peptone was formerly applied to both, and commercial 
" peptone " consists largely of proteoses. 

Protein Tests 

The following are some of the most general tests for 
proteins : 

1. Decomposition Test. — Proteins when subjected to dry 
heat {e.g. in a test tube) give off vapors having an alkaline 



1 86 ELEMENTARY HOUSEHOLD CHEMISTRY 

reaction and a characteristic, disagreeable, " empyreumatic " 
odor — that of burning meat, feathers, leather, hair, wool, etc. 
When the protein is mixed with lime and heated, the odor 
of ammonia is distinctly noticeable. 

Experiment 104. 

Materials : 

Egg albumin, dry. 

Blood albumin, dry. 

Gelatin. 

Casein. 

Quicklime. 

Turmeric paper. 

Red litmus paper. 
Heat a little of each of the proteins in a dry test tube. Note 
the odor. Add quicklime and heat again. Note odor and hold 
turmeric paper and red litmus paper at the mouth of the test tube. 
Also expose turmeric paper and red litmus paper to ammonia gas 
by holding them to the open mouth of the ammonium hydroxide 
reagent bottle. 

2. Xanthoproteic Test (Greek, xanthos — yellow). — Pro- 
teins heated with concentrated nitric acid impart a yellow 
color to the acid, owing to the formation of xanthoproteic 
acid. If the acid be then neutralized with ammonia, the 
color deepens. 

Experiment 105. 

Materials : 

The same proteins as for Experiment 104. 
Sugar. 

Gently heat a little of each of the proteins with concentrated 
nitric acid. Note the coloration. Cool the tube, and then neu- 
tralize the acid with ammonium hydroxide. Heat a very little 
sugar with nitric acid in the same manner as the proteins. Is the 
acid colored by the sugar? Cool and neutralize with ammonia. 
In making the xanthoproteic tests on the proteins notice the dif- 
ference in behavior between gelatin and the other proteins. 
Chemically pure gelatin gives no xanthoproteic test. This test 
is due to the action of nitric acid upon the amino acids of a certain 



THE PROTEINS 187 

class, none of which is yielded by the hydrolysis of pure gelatin. 
Commercial gelatin, however, contains small quantities of other 
proteins. 

3. Millon's Test. Proteins boiled with Millon's reagent 
(prepared by dissolving mercury in its own weight of con- 
centrated nitric acid, diluting with twice the volume of water, 
and allowing to settle) yield a red precipitate which collects 
at the surface of the liquid. 

Experiment 106. 

Materials : 

The same proteins as for Experiment 104. 

Boil small portions of the proteins in test tubes with Millon's 
reagent. Note the difference in behavior between gelatin and 
the others. Pure gelatin gives no Millon's test, this reaction 
being due to an amino acid of the same class as those to which 
the xanthoproteic test is due. 

4. Biuret Test. — Proteins dissolved in strong alkali and 
treated with minute quantities of copper sulphate give a 
violet to blue coloration. The test takes its name from the 
substance with which it was first obtained. Biuret, 
NH 2 . CO . NH . CO . NH 2 , although neither a protein, a 
peptide, nor an amino acid, gives a coloration like that given 
by the proteins. 

Experiment 107. 

Materials : 

The proteins used in Experiment 104. 
Peptone. 
Dissolve a little of each in a 50 per cent solution of potassium 
hydroxide. To a test-tubeful of water add a drop or two of copper 
sulphate solution. Add a few drops of this diluted copper sul- 
phate solution to the alkaline solutions of the proteins. Note 
any differences observed. 



CHAPTER XXXV 

THE PROTEINS. II 

We have seen that the " building stones " which go to 
make up the molecules of proteins are numerous and varied. 
We have also seen that a single pair of these amino acids can 
be joined together into two different products, e.g. glycine 
and alanine into either glycyl alanine or alanyl glycine. 
Remembering, now, that the protein molecules are built up, 
not of two, but of a large number of building stones, we can 
realize that a great many different kinds of protein molecules 
might be constructed, not only by varying the selection of 
the building stones, but also by varying their arrangement. 

Whether this be the explanation or not, it is certainly true 
that the proteins exhibit a remarkable diversity of physical 
properties, particularly as regards their solubilities. It is 
customary to attempt to classify the proteins according to 
their solubilities in a number of solvents. 

The albumins dissolve in water and are coagulated by 
heat. Egg albumin (ovalbumin), milk albumin (lactalbumin), 
and blood albumin (seralbumin) are typical examples. 

The term albumins has been much used as the general class 
name for proteins. The definition here given is that now rec- 
ognized by the leading American and British societies of physi- 
ology and biological chemistry. Other terms formerly used as 
synonyms for the modern term proteins are proteids and 
albuminoids. The societies referred to have agreed to drop the 
word proteid altogether. The English societies also drop albu- 
minoid, while the American societies use it to designate a 
special class of proteins. (See below.) 



THE PROTEINS 189 

Experiment 108. — Coagulation of Egg Albumin. 

Materials : 

Fresh white of egg. 
Thermometer. 
Fill a test tube to the depth of i| to 2 inches with fresh white of 
egg. Put a thermometer into the liquid and place the tube in 
a beaker of cold water over a low flame. Note the temperature 
at which the albumin coagulates (whitens). Express this tem- 
perature in Fahrenheit and in Centigrade degrees. 

It is because of the coagulating effect of heat on albumins 
and on some other classes of proteins that in washing dishes 
which have held uncooked foods, such as milk or eggs, it is 
better to rinse with cold water before applying hot water. 

The globulins are insoluble in water but soluble in dilute 
solutions of the neutral salts of strong acids with strong 
bases. They are, however, insoluble in concentrated solu- 
tions of these same salts. (The albumins are soluble both in 
dilute and in saturated sodium choride and magnesium 
sulphate.) 

Among the globulins are the myosin of meat, the fibrinogen 
of blood (the change of which into fibrin is the cause of blood 
clotting), serum globulin, which remains in solution in the 
serum of blood, and ovoglobulin, a constituent of egg-white. 
Edestin is a globulin found in many plant seeds, including the 
cereals, flaxseed, and hempseed. Legumin is a globulin found 
in peas and beans. 

Experiment 109. 

Materials : 

Hempseed, crushed. 
5 per cent solution of common salt. 
Cover a handful of crushed hempseed with 5 per cent sodium 
chloride and heat to 6o° C. for about half an hour. Moisten 
a filter with hot 5 per cent sodium chloride solution and filter the 
hot liquid through it. Allow the nitrate to cool. Part of the 
edestin crystallizes out on cooling. Filter off a little of this 
crystallized edestin and wash it in test tubes with water. Boil a 



190 ELEMENTARY HOUSEHOLD CHEMISTRY 

little of it with Millon's reagent. Does it behave like a protein? 
Treat three equal portions of the edestin with, respectively, (a) 
distilled water, (b) a 5 per cent sodium chloride solution, (c) a 
saturated sodium chloride solution, warming each to about 6o° C. 
Which of these three liquids is the best solvent for edestin ? 

The most important proteins of the interior of the wheat 
grain (and therefore of white flour) are those which are con- 
tained in the gluten. Gluten, which — as is evident from 
the method of its preparation from flour — is insoluble in 
water, contains as its chief constituents two proteins called 
glutenin and gliadin. Both of these constituents are insoluble 
in water. Glutenin, however, is soluble in very dilute acids 
and alkalies and is representative of a class of proteins known 
as glutelins, which behave similarly. Gliadin is soluble in a 
mixture of alcohol and water containing 60 to 70 per cent of 
the former. It is, however, insoluble in absolute alcohol. 

Experiment no. — Preparation of Wheat Gluten from Flour. 

Materials : 

Wheat flour, strong and not over nine months old. 
Cheesecloth. 

Mix 30 grams flour with 5 cc. water to form a stiff dough. 
Knead in the hand in a stream of running water until the water 
runs through clear. (What constituent of the flour is carried 
out by the water, rendering it turbid?) Examine the residue of 
gluten left in the hand. Note its color and elasticity. The 
quality of flour depends not only on the quantity, but also on the 
quality of the gluten contained in it. The gluten of good flour is 
yellow, tough, and elastic. That of aged flour is grayish and 
" short " or friable. 

Experiment in. — Gliadin. 

Materials : 

Gluten from Experiment no. 
Mortar and pestle. 
Put the gluten from Experiment no in a mortar, cover it with 
a mixture of 5 cc. water and 15 cc. alcohol and rub well with the 
pestle. Filter. To one portion of the filtrate add water, to an- 
other alcohol. What effect does each have ? Explain. 



THE PROTEINS 1 91 

The albuminoids or scleroproteins (from the Greek, 
skleros, hard) are a class of simple proteins characterized by 
great insolubility. They include collagen, the protein of car- 
tilage, skin, and bone ; and keratin, the protein of hair, horns, 
hoofs, nails, etc. Collagen is converted by hydrolysis into 
gelatin which is soluble in hot water, forming a solution which 
sets to a jelly on cooling. Commercial gelatin is usually 
made from bones by treatment with hydrochloric acid, fol- 
lowed by treatment with boiling water or steam. Glue is a 
crude form of gelatin made from hoofs and hide clippings. 
Isinglass is a natural gelatin found in the swimming bladders 
of certain fishes. 

The keratins contain a high proportion of sulphur. Hair 
and wool are therefore characterized by decided tests for 
sulphur — a fact which is used to distinguish these fibers 
from silk, which is also essentially protein but contains no 
sulphur. (See Chapter XL.) 

Experiment 112. 

Materials : 
Sulphur. 
Wool, undyed. 

Egg albumin, raw, coagulated (hard boiled) , or dried. 
Egg yolk, raw or coagulated. 
Silk. 

(a) Prepare sodium plumbite solution by adding sufficient 
sodium hydroxide solution (5 to 10 cc.) to 1 cc. lead acetate solu- 
tion to redissolve (on warming) the precipitate which forms at first. 

(b) Boil a little sulphur with sodium hydroxide solution. Add 
a little of the sodium plumbite. The black precipitate which 
forms is lead sulphide, PbS. 

(c) Boil a small quantity of the wool with sodium hydroxide. 
Add to sodium plumbite solution and boil. Add sufficient water 
to enable you to see through the liquid. Has a black precipitate 
(lead sulphide) formed ? 

(d) Repeat (c) using egg albumin instead of wool. 

(e) Repeat (c) using yolk of egg. 
(/) Repeat (c) using silk. 



CHAPTER XXXVI 

THE FUNCTIONS OF FOOD 

The functions of food are : 

i. To supply building material for the growth and repair 
of body tissue. 

2. To furnish energy for the internal and external work of 
the body and heat to keep the body warm. 

3. To. regulate the physiological processes, i.e. the chemical 
and physical changes occurring in the body. 

I. Food as Building Material 

The human body is composed of the same classes of sub- 
stances as foods. It is made up approximately as follows : 

APPROXIMATE COMPOSITION OF HUMAN BODY 

Per Cent 

Water, about >. . 65 

Proteins, about 18 

Fat, about 12 (varying greatly) 

Carbohydrates, less than 1 

Ash, about 4 to 5. 

The amount of carbohydrates in the body is not only 
very small, but also exceedingly variable. The amount of 
fat is also widely variable and may fall very low without 
interfering with the normal physiological processes. 

Proteins are essential constituents of all living cells, both 
vegetable and animal. There can be no life without them. 
Plants manufacture their own proteins from inorganic ma- 
terials, making use of the carbon dioxide which they obtain 
from the air and of the water and nitrogen compounds which 

192 




Wilbur Olin Atwater. — -1844-1907. 

Distinguished for his researches on the chemistry of nutrition. Professor 
of Chemistry in Wesleyan University, Middletown, Connecticut, from 1873, 
the first director of an American agricultural experiment station, and the first 
Director of the Office of Experiment Stations of the United States Depart- 
ment of Agriculture, Atwater devoted special attention to agricultural chem- 
istry and to problems of human nutrition. Under his direction numerous 
analyses and determinations of digestibility of American food materials were 
made. The respiration calorimeter described in the text was devised for the 
purposes of these nutrition investigations. 



THE FUNCTIONS OF FOOD 193 

they obtain from the soil to build up the large and complex 
protein molecules. 

Animals have not this power of building up proteins from 
inorganic materials. It appears doubtful whether they can 
synthesize them even from simpler organic substances not 
derived from other proteins. For the most part, at any rate, 
they merely take proteins ready-made and convert them 
into other proteins. 

Since animals must have proteins to form and repair their 
body tissues, and since they cannot make proteins except 
from other proteins, it follows that proteins are absolutely 
essential constituents of the food of all animals. However 
generous the supply of carbohydrates and fats, the animal 
cannot thrive nor even continue to live without a constantly 
renewed supply of protein. The term " protein " (from a 
Greek verb signifying to take the first place) is applied to this 
class of compounds on account of its unique and preeminent 
importance in relation to life. 

Some of the ash constituents of food are also of special 
importance as building material. Bones contain a large 
proportion of calcium phosphate. This salt constitutes more 
than half the weight of the dry, or more than one-fourth the 
weight of the fresh, bone. Calcium salts and phosphorus 
compounds are therefore of great importance in foods in 
relation to the growth and maintenance of the skeletal frame- 
work of the body. Iron is an essential constituent of hemo- 
globin, the protein of the red corpuscles of the blood. Hence, 
an abundant supply of iron in the food is important for the 
maintenance of health, and still more so when the blood re- 
quires enrichment ; e.g. in cases of anaemia. 

II. Food as Fuel 

The chief ultimate products of the chemical changes which 
occur in the body are the carbon dioxide given off from the 



194 ELEMENTARY HOUSEHOLD CHEMISTRY 

lungs ; the water excreted by the lungs, skin, and kidneys ; 
and the urea and salts excreted by the kidneys. Urea is a 
nitrogenous organic compound of the formula, CON 2 H 4 , and 
is plainly derived from the proteins. As far as the organic 
foodstuffs are concerned, then, we may summarize the chemi- 
cal reactions of the body as follows : 

Fats and carbohydrates oxidize to carbon dioxide and water. 

Proteins oxidize to carbon dioxide, water, and urea. 

The foregoing paragraph must be understood, not as an adequate 
account of the chemistry of nutrition, but only as the roughest 
outline of the sum of the numerous changes involved. The re- 
actions by which the different classes of foods are digested, ab- 
sorbed, stored, and utilized as fuel are very complicated. Some 
reference to these processes — especially to digestion and absorp- 
tion — will be made later. 

Again, the products enumerated above are by no means all the 
compounds excreted from the body. In addition to water, salts, 
and urea, the urine contains notable quantities of three other 
nitrogenous compounds of importance, namely, uric acid, 
creatinine, and hippuric acid, and also notable quantities of a 
number of sulphur compounds. The bowel excrement (feces), 
although consisting in part of undigested food — more or less 
fermented and putrefied by bacteria — also contains a certain 
proportion of substances derived from the digested and absorbed 
food. Among these are compounds of iron, phosphorus, magnesium, 
and calcium. 

These ultimate products of the chemical changes occurring 
in the body are produced by the combining of the oxygen of 
the air with the elements of the digested and assimilated 
food. And it is to be noted that the products of oxidation of 
the fats and carbohydrates in the body are exactly the same 
as those which are produced by the rapid oxidation, i.e. com- 
bustion, of these substances. 

When food is oxidized in the body, then, the chief chemical 
products are the same as those which would be obtained if 
the food were burned in a stove or in a calorimeter. (See 
p. 52.) For fats and carbohydrates this statement is literally 




Fig. 39. — The Atwater-Rosa Respiration Calorimeter. Interior View. 

From Bulletin 175, Office of Experiment Stations, U. S. Department of Agriculture, 

by permission. 



THE FUNCTIONS OF FOOD 195 

true. In the case of proteins it requires the modification 
that the nitrogen, which in combustion is given off as the 
free element, is excreted from the body combined with a 
certain amount of carbon, hydrogen, and oxygen, chiefly as 
urea, CON 2 H 4 , a compound which can itself be further oxi- 
dized (e.g. by combustion) to carbon dioxide, water, and free 
nitrogen. 

When burned in a furnace, fats and other organic food 
constituents produce heat, a part of which may be converted 
into work by such a device as a steam engine. A fat oxidized 
in the body also produces work and heat, the work-producing 
mechanism being the muscles. 

We can easily measure the quantity of heat which any 
pure foodstuff or any mixed food is capable of producing 
when rapidly oxidized. This measurement can be made in 
exactly the same way as in the case of fuels, i.e. by burning 
a small weighed sample of the food or foodstuff in com- 
pressed oxygen in the bomb calorimeter (see Fig. 32, p. 55), 
and noting the quantity of heat set free. It is also possible 
to measure the quantity of heat set free by a man or an 
animal maintained on a certain diet. This is done by con- 
fining the man or animal to the chamber of an animal calo- 
rimeter — an apparatus which measures the quantity of heat 
given off from his body. 

Figure 39 is an interior view of a " respiration " calorimeter 
designed by the late Professor W. O. Atwater of Wesleyan Uni- 
versity, Middletown, Conn., and Professor E. B. Rosa of the same 
institution, for experiments upon man. This apparatus was so 
constructed that no heat could escape through the walls of the 
chamber. The heat given off by the occupant was absorbed by 
a current of water flowing through the pipes at the top of the 
chamber. 1 The quantity of water flowing through these pipes 
was measured and also its temperature as it entered, and again 

1 In the illustration these pipes are partly, but not entirely, concealed by 
metal "shields," which could be raised or lowered to regulate the rate at which 
the heat was taken up by the water. 



196 ELEMENTARY HOUSEHOLD CHEMISTRY 

as it left, the chamber. The product of the quantity of water 
flowing in a given time and its rise of temperature represented the 
number of Calories given off by the occupant of the chamber. 
The chamber had a tightly sealed window and a porthole or large 
pipe through which food and other materials could be passed in 
and out, the porthole being kept closed at one end whenever it 
was opened at the other. Provision was also made for continually 
renewing the supply of oxygen, and the apparatus owes its name 
of " respiration " calorimeter to the fact that it was so designed 
that not only the heat, but also the amounts of carbon dioxide 
and water produced, and (as later developed) the quantity of 
oxygen used by the subject of the experiment could be measured. 
Experiments with this apparatus were sometimes continued for 
periods of ten or twelve days. 

This apparatus was greatly improved and eventually rebuilt 
by Dr. F. G. Benedict. Figure 40 gives a view of one form of 
apparatus now in use, showing the exterior of the respiration 
chamber and the apparatus used in measuring the heat given off 
and the carbon dioxide and water excreted by the occupant of the 
chamber. An observer is shown seated at the observer's table, 
a post which is manned night and day during the course of an 
experiment. This observer is making the temperature observa- 
tions and so controlling the instrument that no heat can pass 
through the walls of the respiration chamber. In front of the 
observer is a hanging support for the galvanometer, an electrical 
instrument used in the temperature measurements. On the floor 
in front of the observer (at the right of the picture) is a rack or 
table holding the apparatus through which the circulating air is 
passed for purification and analysis before being returned to the 
respiration chamber. Behind the observer's platform (i.e. to the 
reader's left) near the floor is a large cylindrical vessel in which 
the water, which passes through the pipes in the chamber to absorb 
the heat, is collected and weighed. And on the extreme left of 
the picture a second experimenter is seen talking through a tele- 
phone to the man inside the chamber who is serving as the subject 
of the experiment. 

When such measurements are made, it is found that the 
quantity of heat produced by the oxidation of a fat is exactly 
the same when this oxidation takes place slowly in the human 
body as when it takes place instantaneously in the bomb 



THE FUNCTIONS OF FOOD 197 

calorimeter. The same is true of a carbohydrate such as 
starch or sugar. The quantity of heat produced by the 
oxidation of a protein in the body is less than that produced 
by the combustion of the protein in the bomb ; but the dif- 
ference is just the quantity of heat yielded by the combus- 
tion of that quantity of urea and other nitrogenous end 
products which would be formed in the body from the given 
quantity of protein. In other words, if we were to allow 
the oxidation of the protein to go on in the body of the man 
in the respiration calorimeter and then burn in the bomb 
calorimeter the excreta of the man, the total heat obtained 
would be the same as if we had burned the protein directly 
in the bomb calorimeter. 

Making allowance for the average quantities of each 
class of foodstuffs lost in digestion {i.e. excreted in the feces), 
it is found that a pound of carbohydrate in the food yields 
about 181 5 Calories, and a pound of protein the same; but 
a pound of fat yields 4080 Calories. 

One pound of fat is therefore equal in fuel value to 2 J pounds 
of either protein or carbohydrate. 

Stated according to the metric system of weights these 
fuel values are : 

Carbohydrates and proteins 4 Calories per gram 
Fats 9 Calories per gram 

When muscular work is done, the heart beats more rapidly 
and the breathing becomes both faster and deeper. The 
result is a quickening of the oxidation processes in the body. 
A larger quantity of assimilated food material is oxidized in 
a given time, and of course a larger quantity of heat is pro- 
duced. But the quantity of heat given off from the body 
does not now amount to 181 5 Calories for each pound of 
protein and each pound of carbohydrate and 4080 Calories 
for each pound of fat oxidized, for a part of the " fuel value " 
of the food is converted into mechanical work. 



198 ELEMENTARY HOUSEHOLD CHEMISTRY 

This partial conversion of the fuel value or energy of the 
food into work is accomplished by the muscles of the body 
in a way that is not fully understood. In the steam engine 
all the energy of the fuel is first converted into heat and then 
a part of the heat is converted into work. In the muscles 
only a part of the original energy is converted into heat. 
The remainder is apparently converted directly into work. 
As much as one- fifth of the fuel value of the foodstuffs oxidized 
may be converted into work by the engine of the human 
body, i.e. the muscular system. The work done may be re- 
converted into heat, and when this is done, the total quantity 
of heat produced — that evolved directly as heat plus that 
produced as work and then converted into heat — is equal 
to 181 5 Calories per pound of carbohydrate and protein and 
4080 Calories per pound of fat oxidized. 

In some of the experiments with the respiration calorimeter 
the man in the chamber turned the wheel of a stationary 
bicycle which was attached to an electric dynamo, the current 
produced by which was passed through an incandescent 
electric light bulb. This device enabled the experimenters 
to estimate the quantity of work done and at the same time 
provided for the reconversion of the work into heat within 
the calorimeter. 

III. Food as a Regulator of Physiological Processes 

Much less is definitely known about this function of food 
than about the other two. It is certain, however, that some 
foods have a greater tendency to stimulate the activity of 
the intestines than have others. In other words some foods 
are laxative, others constipating. Among the laxative foods 
are fruits, green vegetables, and the coarser cereal products. 
Fruits and green vegetables contain much water and ash 
constituents or " mineral matter " (salts of organic as well 
as of inorganic acids). The outer portion of the wheat 



THE FUNCTIONS OF FOOD 199 

kernel (the bran) contains not only a larger proportion of 
mineral matter, but also a larger proportion of cellulose — a 
carbohydrate which largely escapes digestion. Cellulose is 
also a prominent constituent of green vegetables, such as 
celery, lettuce, radishes, asparagus, etc. The laxative effect 
of coarse foods is commonly regarded as due to their mechan- 
ical stimulation of the intestinal lining. But it has been 
shown in experiments upon cows that wheat bran, which in 
its natural state contains the potassium, magnesium, and cal- 
cium salts of an organic acid, called phytic acid, loses its 
laxative effect when these salts are removed from it. It has 
been found that persons living exclusively or very largely on a 
diet of rice suffer from the disease beriberi if the bran of the 
rice has been polished off. While, therefore, the mechanical 
effect of coarse foods in stimulating the bowels may be 
important, it seems probable that the chemical effects of 
certain foods may be equally or in some cases even more 
important. 

Certain of the body fluids, such as the gastric juice, the 
digestive fluid of the stomach, have an acid reaction ; certain 
others, such as the saliva, the bile, and the blood, have an 
alkaline reaction. It is necessary to health that the acidity 
of the former and the alkalinity of the latter should remain 
within certain limits. The gastric juice, for example, must 
not become either neutral or too strongly acid. Now in 
the oxidation processes which go on in the body certain 
constituents of food are converted into acid products, cer- 
tain others into alkaline products. Thus in the oxidation 
of proteins, sulphuric acid is produced from the sulphur 
of the protein molecule, while the phosphorus of phospho- 
and nucleo-proteins and of phosphorized fats, such as 
lecithin, yields phosphoric acid. On the other hand, the 
salts of all organic acids oxidize to bicarbonates, which may 
act as alkalies. 

An excess of acid-producing constituents in the food is 



200 ELEMENTARY HOUSEHOLD CHEMISTRY 

apt to lead to physiological disturbances. The foods in 
which acid-producing elements predominate are meats, eggs, 
and cereals. In vegetables, fruits, and milk the base-form- 
ing elements predominate. 

For a fuller discussion of the chemistry of nutrition the reader is referred to 
Sherman's " Chemistry of Food and Nutrition." New York, 1911. 



1 

1 

1 



■ 

CHAPTER XXXVII 
THE DIGESTION OF FOOD 

In order to reach the tissues it is to repair or the muscles 
for whose activities it is to serve as fuel material, the food 
taken into the alimentary canal must be absorbed into the 
circulating fluids of the body, the blood and lymph. To get 
into these fluids it must pass through the membranous 
envelopes of the vessels containing them, the capillaries 
(small blood vessels) and lacteals (lymph vessels). These 
vessels are especially abundant in the folds and villi of the 
small intestine, which is the chief seat of absorption. Absorp- 
tion, however, occurs also to a slight extent in the stomach 
and to a considerable extent in the large (lower) intestine. 

Now, chemical compounds of different classes show strik- 
ing differences in their ability to pass through membranes of 
a colloidal nature, such as make up the linings of the diges- 
tive organs and the envelopes of the capillaries and lacteals. 
Such differences are illustrated in the following experiments, 
although it is only fair to premise that some substances 
which do pass through the membranes used in the experi- 
ments do not pass through the living membranes of the 
digestive organs. 

Experiment 113. 

Materials : 

Parchment filters or parchment tubing. 
Glass jars or large beakers. 
Glucose (dextrose). 
Fructose (levulose). 
Cane sugar. 
Maltose. 
Dextrin. 

Starch paste, prepared as in Experiment 101 (p. 170). 

201 



202 



ELEMENTARY HOUSEHOLD CHEMISTRY 




Put solutions of the carbohydrates named above (about one 
part carbohydrate to ten parts water) into the parchment filters 
or into pieces of the tubing, being careful to get none of the solu- 
tion on the outer surface of the parchment. Add a drop of chloro- 
form to each to prevent the growth of microorganisms. 

Suspend the papers in jars or beakers of distilled water. If 
tubing is used, both ends should be suspended above the surface 

of the water, making a U-shaped 
tube dipping beneath the surface 
of the water. (See Fig. 41.) Allow 
to stand overnight. Then care- 
fully withdraw portions of the 
outer liquids from the bottom of 
the jars with pipettes and test for 
the carbohydrates used, making 
parallel tests with some of the 
liquids from the interior of the 
parchment vessels. For tests see 
your record of Experiments 99 to 
101. Dextrin is tested for by add- 
ing the liquid to a solution of iodine 
Fig. 41. — Apparatus for the study diluted so as to appear yellow. 
of the diffusibility of carbohydrates Dextrin changes the color to red. 
through parchment paper. -^ 1 i 1 

Parchment paper is made by 

dipping paper into strong sulphuric acid and then thoroughly 
washing. This treatment greatly reduces the porosity of the 
paper by converting some of the cellulose into a more bulky sub- 
stance. (See Experiment 139, p. 232.) 

Experiment 114. 

Materials : 

Goldbeater's skin. 

The same carbohydrates as in preceding experiment. 

Select test tubes with evenly flanged tops ; heat the closed ends 
in the flame and blow them out while soft, thus forming a tube 
open at both ends. Cut the goldbeater's skin into squares of 
about i\ inches and bind these tightly over the flanged ends of the 
tubes with thread. To make sure that the tubes are tightly closed 
with the skin, fill them with water. The water will gradually 
pass through the skins, but will not flow in a stream nor drop rapidly 
if the skin is perfect and is properly bound to the tube. 

Fill these tubes about three-fourths with the carbohydrate 



THE DIGESTION OF FOOD 203 

solutions used in Experiment 113, being careful to avoid wetting 
the outside surface. Place them in beakers of distilled water, and 
allow to stand overnight. Pipette off portions of the outer liquids 
from the bottom of the beakers and test for the carbohydrates as 
in the preceding experiment. 

Goldbeater's skin is made from the inner lining of the intestines 
of cattle. 

The above experiments show that colloidally dissolved 
carbohydrates will not pass through the membranes used, 
while the substances in true solution (the crystalloids) do 
pass through. From the observations which have been 
made upon living animals, however, it appears that even 
some of the crystalloid substances cannot pass through the 
envelopes of the blood and lymph vessels. The substances 
which will not pass through are those made up of large mole- 
cules. .Thus in some cases monosaccharides pass through 
but disaccharides do not. 

It would appear from experiments upon animals that, as a 
preliminary to absorption and utilization, all carbohydrates 
must be changed into monosaccharides. Similarly, fats are not 
absorbed until converted into fatty acids (or salts of fatty acids, 
i.e. soaps) and glycerol ; and proteins not until converted into 
amino acids and, perhaps, relatively simple polypeptides. 

It will be noticed that the chemical changes w r hich all 
these nutrients undergo preliminary to absorption are hydro- 
lytic. In other words, all nutrients incapable of direct 
absorption are converted into absorbable nutrients by re- 
action with water. But this hydrolysis of the complex 
molecules of polysaccharides, proteins, and fats takes place 
only in contact with certain organic catalytic reagents, 
known as enzymes or " digestive ferments." 

These enzymes are contained in the digestive juices se- 
creted by cells in the linings of the digestive organs or by 
glands which communicate with those organs. The digestive 
juices are : 



204 



ELEMENTARY HOUSEHOLD CHEMISTRY 



(i) The saliva, secreted by glands in or delivering their 
secretions into the mouth. 

(2) The gastric juice, secreted by certain ^rells of the stomach 
wall, chiefly in the middle division of the stomach. 

(3) The pancreatic juice, secreted by the pancreas and de- 
livered into the small intestine (duodenum). 

(4) The bile, secreted by the liver and delivered into the 
small intestine. 

(5) The intestinal juice, secreted by certain cells of the 
intestinal lining. 

All of these but the bile are known to contain enzymes 
that promote the hydrolysis of organic nutrients. Of such 
enzymes the following are well known : 

HYDROLYTIC ENZYMES OF THE DIGESTIVE FLUIDS 



Digestive 
Secretion 


Enzyme 


Seat of Action 


Compounds 
Affected 


Products (or 
Chief Products) 


Saliva 


Ptyalin 


Mouth and 
cardiac (an- 
terior) end 
of stomach 


Starch 


Dextrin and 
maltose 


Gastric juice 


Pepsin 


Pyloric (pos- 
terior) end 
of stomach 


Proteins 


Proteoses and 
peptones 




Gastric 


Stomach 


Emulsified 


Fatty acids 




lipase 




fats, such 
as cream 


and glycerol 


Pancreatic 


Amylopsin 


Intestines 


Starch and 


Maltose 


juice 






dextrin 






Trypsin 


Intestines 


Proteins 


Proteoses, pep- 
tones, poly- 
peptides, and 
amino acids 




Steapsin 


Intestines 


Fats (emul- 
sified by 
bile) 


Fatty acids 
and glycerol 


Intestinal 


Sucrase 


Intestines 


Sucrose 


Glucose and 


juice 


(invertase) 






fructose 




Maltase 


Intestines 


Maltose 


Glucose 




Lactase 


Intestines 


Lactose 


Glucose and 
galactose 




Erepsin 


Intestines 


Proteoses 
and pep- 
tones 


Amino acids 
and ammonia 



THE DIGESTION OF FOOD 205 



EXERCISES 

1. Classify these enzymes as (1) Amylases, (2) Disaccharases, 
(3) Lipases, (4) Proteases. 

2. Write equations for the hydrolysis of: (a) Sucrose, (6) 
Tristearin, (c) Glycyl glycine. 

The following experiments will serve to illustrate the effects 
of enzymes : 

Experiment 115. — Action of Ptyalin on Starch. 

Materials : 

Starch solution. 

Prepare a starch solution as in Experiment 101 (p. 171), dilute 
it with two or three times its volume of water, cool to the tem- 
perature of the hand, add a little of your own saliva, mix well 
and place in a beaker of water at the temperature of the hand 
(about 3 8° C). After five or ten minutes pour off a little of 
the liquid into a test tube containing iodine solution. If this test 
shows starch to be still present, add more saliva, allow the test 
tube to stand longer in the beaker, and repeat the iodine test at 
intervals. When this test shows all the starch to have been trans- 
formed, pour off a little of the liquid remaining in the test tube 
into Fehling-Benedict solution and boil. What kind of sub- 
stance has been formed from the starch ? For comparison a little 
of the starch solution without saliva may be similarly treated and 
tested. 

Experiment 116. — Action of Proteolytic Ferments (Proteases) on 

Fibrin. 

Materials : 
Fibrin. 1 

Pepsin solution. 
Trypsin solution. 

0.4 per cent solution hydrochloric acid. 
1.0 per cent solution sodium carbonate. 

1 The fibrin, pepsin, and trypsin may be most conveniently bought in the 
dried condition. The fibrin should be soaked in water for an hour or more 
before beginning the experiment. For the pepsin and trypsin solutions 0.1 
gram of the commercial ferments are to be dissolved in one liter of water. If 
preferred, fresh fibrin may be made by whipping freshly drawn ox blood with 
twigs to promote clotting and then washing the clot with cold water until the 



206 ELEMENTARY HOUSEHOLD CHEMISTRY 

Into each of six test tubes put a piece of fibrin. Add respectively 
(i) 5 cc. water, (2) 5 cc. pepsin solution, (3) 5 cc. 0.4 per cent 
hydrochloric acid, (4) 2.5 cc. pepsin solution and 2.5 cc. 0.4 per 
cent hydrochloric acid, (5) 5 cc. trypsin solution, (6) 2.5 cc. 
trypsin solution and 2.5 cc. sodium carbonate solution. 

Set the test tubes (labeled) in an empty beaker or in a suitable 
rack and place in a water oven at 40 C. Examine after 24 hours. 
In which of the tubes has the fibrin been dissolved? Filter 
and make the biuret test on a portion of the nitrate. Boil 
another portion. What do you infer from the results? Does 
the hydrochloric acid alone affect the fibrin in any way? Is the 
action of the pepsin affected by the addition of hydrochloric acid ? 
Is that of the trypsin affected by the sodium carbonate? 

It is extremely difficult to separate an enzyme from the 
substances accompanying it, and it is also difficult to deter- 
mine whether any given preparation is to be regarded as 
pure. The best preparations that have been made, however, 
resemble the proteins in composition and behavior, and it is 
probable that enzymes are themselves proteins. A pepsin 
preparation has been made which was capable of digesting 
500,000 times its weight of fibrin ; also a pancreatic amylase 
(amylopsin) capable of digesting 1,000,000 times its weight 
of starch. 

red color is gone. Pepsin solution may be prepared fresh by extracting the 
finely cut mucous membrane of a pig's stomach for 24 hours either with 0.4 per 
cent hydrochloric acid at 38-40 C. or with glycerin at room temperature. 
Fresh trypsin solution can be made by extracting the finely divided pancreas of 
the pig or sheep for three days with water containing 5-10 cc. of chloroform or 
with glycerin. The 0.4 per cent hydrochloric acid may be made from the 
reagent (2 N) dilute hydrochloric acid by diluting with 18 times its volume of 
water. The sodium carbonate solution may be made directly by dissolving 1 
gram anhydrous sodium carbonate in 100 cc. water. 



CHAPTER XXXVIII 

FOODS OF VEGETABLE ORIGIN 

Tables giving the average composition and fuel value 
of American food materials are given in Appendix A. Table I 
(pp. 271-277) comprises a classified selection of foods of vege- 
table origin. The last four columns of the table give the es- 
sential information about the edible portion of each food. 
The first column gives the percentage of refuse in the food as 
purchased. In comparing costs this must, of course, be taken 
into consideration. Thus, the 100-Calorie portion of the 
edible part of a banana (the first item in the table) is 3.6 
ounces. But the average amount of refuse in a banana as 
purchased is 35 per cent. Thus with every 65 ounces of 
edible banana we purchase 35 ounces of banana peel. The 
100-Calorie portion of banana as purchased is therefore 100 
sixty-fifths of 3.6 ounces, which is equal to 5.5 ounces. 

EXERCISES 

1. Calculate similarly the 100-Calorie portion of the follow- 
ing foods as purchased : (a) Grapes, (b) Lemons, (c) Squash, 
(d) Green peas, (e) Butternuts. 

2. From the percentage composition of ten selected foods, as 
given in the second to fifth columns of the table, calculate the 
number of Calories per pound, the number of ounces yielding 100 
Calories and the number of Calories out of every 100 yielded by 
proteins, fats, and carbohydrates, respectively. For methods see 
Appendix A, pp. 268-270. 

3. From the percentage composition of the following foods 
calculate as in Exercise 2 the number of Calories per pound, the 
weight of the 100-Calorie portion in ounces, and the distribution 
of the 100 Calories among the three classes of organic nutrients ; 
also in ounces the 100-Calorie portion of the food as purchased : 

207 



208 



ELEMENTARY HOUSEHOLD CHEMISTRY 



IOO- 

Calorie 
Portion 
as Pur- 
chased 








O 
i— i 

H 

P< 
O 
Ph 

w 
hJ 

pp 

1— 1 

Q 

w 


o 

ft 

CO 

W 

a 

o 

1-1 

< ' 
U 






+J 

&h 




o 

M 

Ph 




IOO- 

Calorie 
Portion 
Ounces 




Calories 

Per 

Pound 




Ph 

o 

H 

u 

w 

Ph 


is 


t 1 N 

■•o do 

M iH 


CO 
M 


^ <n 0\ u-> ro r^ 

« d N H O CO 

U"5 t~^ M VQ 


a! 


1 1 o 


o 


H O <N tO Tj" LO 

O H h O O co 

M 


"u 
o 

>H 

Ph 


>i MD o 


vO 


lO N <t OO OJ >st 


H N 


CO 


H U") VO CS H !>. 


|H 

0) 


lO Ov c> 
00 00 t>. 


On 


t-^ ^ vO "O MD co 
CO 00 co -rf HH <^- 
O H CO O H 


W 
Ph* 


o o 




Q 
O 
O 

Ph 




Apricots . . . 
Muskmelons 
Artichokes . . 


43 
rn 

d 
+-> 
O 

CJ 

o 

d 

C/3 


Brussels sprouts 
Lentils, dried 
Buckwheat flour 
Oatmeal, boiled . 
Oatmeal gruel . 
Jumbles . . . 



FOODS OF VEGETABLE ORIGIN 209 

The most marked general characteristic of vegetable 
foods is the large proportion of carbohydrates contained in 
them. If we except olives and chocolate, which contain 
a large proportion of fat (olive oil and cocoa butter) ; nuts 
and oatmeal, which are rich in both fat and protein ; and 
mushrooms, lettuce, and the legumes, which are rich in pro- 
tein, we may say that all the vegetable foods have over three- 
quarters of their total fuel value in the form of carbohydrates. 
In many, such as potatoes and all products of the cereal 
grains, the predominating carbohydrate is starch. In others, 
such as fruits, sugars and pectins are predominant. In a 
few, such as green vegetables and coarse roots, e.g. turnips 
and radishes, cellulose abounds. But carbohydrates in some 
form characterize them all. 

Experiment 117. 

Materials : 
Potatoes. 

(a) Pare and grate one quarter of a potato. Add a little water 
and filter. Boil a portion of the filtrate. Make the biuret 
test on another portion. What kind of substance have you thus 
detected in potato juice? 

(b) Add a portion of the filtrate to Fehling-Benedict solution 
and boil. What kind of substance does this test show the potato 
juice to contain ? 

(c) Place the potato pulp in a cheesecloth bag. Allow a 
stream of water to run through the bag into a beaker and knead 
the bag. Continue until the water runs through clear. Allow 
the contents of the beaker to settle. Examine the residue left 
in the bag. It consists mainly of " fiber " or " cellulose." 

(d) When the contents of the beaker have settled, remove a 
portion of the sediment, boil it with water, cool, and test with iodine. 
What do you infer that the sediment was ? 

What three kinds of carbohydrates have you detected in the 
potato ? 

The water in the potato may be determined as in Expt. 96 
(p. 163), and the ash by burning the dried material in the dish, 
avoiding heating above dull redness. For average results consult 
Table I, p. 272. The ash averages 1.0 per cent. 
p 



2IO ELEMENTARY HOUSEHOLD CHEMISTRY 

Experiment 118. 

Materials : 

Carrots. __ 

Beets. 
Grate a carrot. Test a portion of the pulp for proteins, using 
two appropriate tests. Digest a portion of the pulp with cold 
water ; filter and test the filtrate for (a) reducing sugars, (b) sucrose. 
(How?) Boil a portion of the pulp with water, cool, and test for 
starch. 

Make the same tests on beets. 

Experiment 119. 

Materials : 
Orange. 
Apple. 
Test some of the orange juice and some of the apple juice for 
reducing sugars. Also test the juices with litmus. Test the pulp 
for starch by boiling with water, cooling, and adding iodine. 

Experiment 120. 

, Materials: 

Oatmeal. 

Beans, ground. 

Walnuts, ground. 
Test each for starch and for proteins. Shake a portion of each 
with benzine, filter through a dry filter on to a clean watch glass, 
set in a warm place to evaporate the benzine. If a residue remains, 
add Sudan III solution and warm water. What do you infer from 
the result ? 

Very few of the foods of vegetable origin contain as large 
a proportion of proteins as is demanded by the older " dietary 
standards," which, in general, require 15 to 16 Calories out 
of every 100 to come from protein. Reference to the tables 
will show that mushrooms, peas, beans, peanuts, butternuts, 
cocoa, and oatmeal have more than this proportion of pro- 
tein. So also have several of the foods known as " vege- 
tables " in cookery — including most of those derived from 
the stalks and leaves of plants, and also pumpkins, tomatoes, 
and radishes. In the case of these latter, however, it is to 



FOODS OF VEGETABLE ORIGIN 21 1 

be remembered that a considerable proportion of the nitrogen 
calculated as protein is really not in true protein compounds, 
and that, being bulky foods containing much water, these 
" vegetables " do not, as a rule, contribute a very large pro- 
portion of the total fuel value of the diet. 

On the basis of the more recently proposed " dietary 
standards " — not only the radically low protein one of 
Chittenden but also the more moderate standards such as 
that of Langworthy x — a much larger number of foods of 
vegetable origin contain an adequate proportion of proteins. 
These would include wheat flour and bread, potatoes and most 
varieties of roots, and the greater number of varieties of nuts. 

As a rule the quantity of fat in vegetable foods is small. 
Conspicuous exceptions are the nuts (including peanuts), 
chocolate and its derivative cocoa, and olives. The germs of 
cereal grains are also rich in fat. But in the manufacture 
of some commercial foods from cereals — particularly in 
that of white flour and cornmeal — the germ is removed 
because of the tendency of the fat to become rancid and thus 
cause deterioration of the product. Oatmeal and rolled oats, 
on the other hand, contain fat sufficient to yield a fuel value 
equal to that of their proteins, and are thus the best balanced 
of all the cereal products. In cooking cereals and vegetables 
it is common to add fat to compensate for the natural defi- 
ciency of such foods in this nutrient. Hence the division of 
the table entitled " Baked Foods " (pp. 274-5) shows in many 
instances a liberal proportion of fats to carbohydrates. 

As to the quantities of the important mineral elements — 
calcium, phosphorus and iron — that they contain, foods of 
vegetable origin differ greatly. Table II in Appendix A 
(pp. 278-9) gives the quantities of these three elements (the 
calcium and phosphorus stated in terms of milligrams of 
their oxides, the iron as milligrams of the element) contained 
in the 100-Calorie portion of a number of vegetable foods, 

1 Sherman's "Chemistry of Food and Nutrition," Chapter VIII. 



212 



ELEMENTARY HOUSEHOLD CHEMISTRY 



classified as in Table I. To compare the foods on the basis 
of equal weights, one must divide these quantities by the 
weight of the ioo-Calorie portion. Thus^while per ioo- 
Calorie portion spinach is much richer than ripe beans in 
all three of these constituents, it is much poorer in all per 
ioo grams or per pound. 





Spinach 


Beans 


ioo-Calorie portion in grams 
CaO per ioo- Calorie portion 

P2O5 per 1 00- Calorie portion 
P2O5 per 100 grams . . . 
Fe per ioo-Calorie portion 
Fe per 100 grams . . . 






412 
370 mg. 

89 mg. 
540 mg. 
129 mg. 
13-3 mg. 

3.2 mg. 


29 

63 mg. 
217 mg. 
336 mg. 
1 140 mg. 
2.0 mg. 
6.9 mg. 



Among foods of its own class, however, spinach stands 
conspicuously high as regards its content of iron and phos- 
phorus and fairly high also as regards calcium. Cauliflower 
and celery, however, are much richer in calcium. The legumes 
are also rich in all three of the important mineral elements. 
Among the cereals, those containing the outer layers of the 
grain (oatmeal and Graham flour) are richest in all three of 
these elements. 

An adequate supply of the bone-forming materials, lime 
and phosphoric acid, is of special importance in children's 
dietaries. Table II shows that green vegetables and roots 
(especially turnips, carrots, and parsnips) are conspicuously 
rich in these ingredients. Some fruits also (for example, 
oranges) contain much calcium in the form of organic salts. 

As noted in Chapter XXXVI (p. 200) the cereals contain 
a small excess of acid-forming constituents, while in the vege- 
tables, fruits, and legumes base-forming elements predomi- 
nate. 



CHAPTER XXXIX 

FOODS OF ANIMAL ORIGIN 

If the foods of vegetable origin are to be regarded as mainly 
carbohydrate foods, those of animal origin are, on the whole, 
to be regarded as protein and fat foods. To be sure, honey 
contains practically no nutrient but the carbohydrates, 
glucose, fructose, and a little sucrose ; but it is exceptional. 
Other than honey, the only animal foods containing any 
proportion of carbohydrates worthy of consideration are 
milk and some of its products (particularly skim milk, butter- 
milk, and whey), and shellfish, such as oysters and clams. 
Liver, cream, cheese, and shad roe contain minor quantities 
of carbohydrates. All the other animal foods are made up 
(as regards their organic nutrients) almost exclusively of 
protein and fat. 

The proportions of these two classes of nutrients, protein 
and fats, vary widely in the different animal foods. Egg- 
white is fat free, consisting of pure protein matter with some 
ash and much water. Gelatin is all protein also, but, curi- 
ously enough, it is not by itself capable of building muscular 
tissue — a fact that is probably related to the absence of 
certain amino acids (particularly tyrosine and tryptophane) 
from among its hydrolysis products. The protein of frogs' 
legs and of codfish yields over 95 per cent of the total fuel 
value of these foods. On the other hand, the energy of fat 
pork, of cream, and of butter comes nearly all from the fat ; 
and lard and tallow are, of course, practically pure fats. 

Meats vary greatly in composition with the variety, the 
cut, and the condition of the animal when killed. The 
tongue, breast, and shoulder, for instance, are much more 
muscular than the ribs, loin, and rump. Hence we find a 

213 



214 ELEMENTARY HOUSEHOLD CHEMISTRY 

larger proportion of protein in cuts of the former class, and 
a larger proportion of fat in those of the latter. 

Table III of Appendix A (p. 280) gives the average com- 
position and nutritive value of several varieties and cuts of 
meats. Table IV (p. 282) illustrates how widely the same 
cuts may vary according as they are from fat or lean ani- 
mals. The figures given in the latter table are not the ex- 
treme values found in individual cuts of meat, but are in each 
instance the average of the results of analysis of several 
pieces classed as fat, medium fat, lean, etc. It will be 
observed that as the percentage of fat in the meat increases 
the percentages of water and protein decrease. But even 
the leanest meat is not entirely devoid of fat. 

Experiment 121. 

Materials : 
Lean beef. 

Remove all visible fat from the beef ; then cut it up into fine 
pieces or put it through a mincer. Place some of the minced meat 
in a dish, cover with alcohol, and knead to extract the water from 
the tissues. Pour off this alcohol, add more, and knead again. 
Pour off the alcohol, add benzine, and knead or shake. Filter off 
the benzine, allow it to evaporate, and test the residue for fat with 
Sudan III solution. 

Experiment 122. 

Materials : 
Lean beef. 

Mince the beef, put it in a cheesecloth bag, and knead in running 
water until the tissues are white. Apply Millon's test and the 
xanthoproteic test to these tissues. 

Reference to Table III (Appendix A) will show that pork, 
mutton, and lamb are, as a rule, fatter than beef, and beef is 
usually fatter than veal. The average fore quarter or hind 
quarter of beef yields out of every 100 Calories about 30 
Calories from protein and 70 Calories from fat. The fore 
quarter or hind quarter of mutton yields about 20 Calories 



FOODS OF ANIMAL ORIGIN 215 

from protein and 80 from fat. The average pork ham yields 
about 17 Calories from protein to St, from fat, and the average 
side of pork only 7 Calories from protein out of every 100. 
Average veal, on the other hand, has about half of its fuel 
value in the form of protein. 

When the fat is largely trimmed off by the butcher or 
cook or rejected at table, there is, of course, not only a great 
loss of fuel value, but the proportions of protein and fat in 
the food actually eaten are greatly altered. Rejected fat 
is not included in the refuse as estimated in the tables. 
These tables, therefore, give higher energy values to the meats 
than are usually realized from them. 

Table V (Appendix A, p. 283) gives the average composi- 
tion and nutritive value of fish of several varieties. 

Most fish have over half their fuel value in the form of 
protein. A few of the fatter varieties, such as sardines, 
salmon, trout, shad, and eels, have a little less than half 
(43 to 50 per cent) of their fuel value in the protein form, 
while the leanest varieties, such as cod, haddock, and pickerel, 
may have as much as 90 Calories out of every 100 from 
protein. 

Table VI (Appendix A, p. 284) gives the average composi- 
tion and fuel value of dairy products. Here a column must 
be provided for the carbohydrates, viz. the lactose. In whole 
milk, evaporated milk, and milk powder this provides about 
29 per cent of the total fuel value. In the dairy products 
richer in fat (butter, cream, and cheese) the lactose plays a 
minor part. In skim milk, buttermilk, and whey, on the 
other hand, it becomes the most prominent nutrient. In 
sweetened condensed milk the cane sugar added constitutes 
about four fifths of the total carbohydrates and the milk 
sugar only one fifth. 

Table VII (Appendix A, p. 285) gives the composition and 
nutritive value of miscellaneous foods of animal origin. Eggs, 
it will be noted, are protein and fat foods. The whites, how- 



2l6 ELEMENTARY HOUSEHOLD CHEMISTRY 

ever, contribute protein only, while the yolks have twice 
as much fat as protein by weight and between four and five 
times as much by calories. Shad roe and the shellfish, in 
spite of the presence of carbohydrates (glycogen), are highly 
nitrogenous foods. The shellfish, white of eggs, and frogs' 
legs have high ioo-Calorie portions on account of their high 
water content and low fat content. In other words, altnough 
their dry matter is highly nitrogenous, they contain only a 
small amount of dry matter per pound. 

Meats are poor in calcium, and eggs contain only a moderate 
amount. See Table VIII (Appendix A, p. 286). Milk, how- 
ever, is extraordinarily rich in this element, and the same is 
true of some of its products, especially cheese and buttermilk. 
As pointed out by Sherman, a quart of milk contains rather 
more calcium than a quart of clear, saturated limewater, 
and one would need to take 25 hundred-Calorie portions of 
round steak and white bread to get as much calcium as one 
could obtain in 1 hundred-Calorie portion of whole milk or 
of cheese. 

The majority of animal foods contain a liberal supply 
of phosphorus. In egg yolk this exists in the form of phos- 
phorized fats and phospho-proteins — forms in which it is 
more readily assimilated than in the inorganic phosphates. 
In meat and fish it is mainly in the inorganic forms. In milk 
it is present in both inorganic and organic forms ; in cheese, 
chiefly in organic combination, viz. as casein. 

Iron in readily assimilable form is abundant in egg yolk. 
It is from the organic iron compounds contained in the yolk 
that the hemoglobin of the chick's blood is formed, and there 
is good reason to believe that it serves a similar purpose in 
the human diet. The iron in lean meats is chiefly present as 
hemoglobin in the blood retained in the tissues. It is, how- 
ever, not certain that this iron is as useful in the human diet 
as that of eggs, milk, and vegetables, because hemoglobin 
is not readily digested. 



FOODS OF ANIMAL ORIGIN 217 

Milk and eggs are especially valuable foods for children, 
not only on account of their protein content and the emulsi- 
fied condition of their fats, but also on account of the kinds 
of mineral matter they contain. Per 100-Calories of fuel 
value milk contains far more calcium than any other food. 
It is also rich in phosphorus, being surpassed, however, in 
this respect by a few foods, such as lean beef and beans. 
Eggs are also among the richest foods in phosphorus content, 
and contain a fair proportion of calcium as well. 



CHAPTER XL 

TEXTILE FIBERS OF ANIMAL ORIGIN. WOOL AND 

SILK 

Textiles for clothing and for household furnishings can 
be made from any kind of fiber, natural or artificial, which 
has sufficient length, strength, and elasticity. The mineral 
kingdom furnishes some such fibers — asbestos, spun gold 
and silver, and spun glass. On account of their costliness 
and other defects, however, the mineral fibers find only 
limited application. Both the vegetable and the animal 
kingdoms, on the other hand, yield us fibers of very wide 
utility. 

The animal fibers are of two classes, viz. (i) Hair fibers, 
of which wool is by far the most important ; (2) Silk fibers. 
Both classes are composed. of protein substances, but the 
silks are sulphur-free, while the hair-fibers, being keratins, 
are rich in sulphur. (See Expt. 112, p. 191.) 

Experiment 123. 

Materials : 
Wool. 
Silk. 
Burn a little of each kind of fiber in a flame, noting the odor and 
the shape which the end of the fiber assumes. Heat portions in 
small, dry test tubes and test the evolved gases for ammonia with 
red litmus paper, and for hydrogen sulphide gas, H 2 S, with paper 
moistened with lead acetate solution. Hydrogen sulphide reacts 
with lead acetate to give lead sulphide, PbS, which is black. 

Make the xanthoproteic test (Expt. 105, p. 186) and Millon's 
test (Expt. 106, p. 187) on other portions of the wool and silk. 

218 




Fig. 42. — Wool fibers magnified. 

From Kinne and Cooley's " Shelter and Clothing," 
by kind permission. 



Fig. 43. — Silk fibers magnified. 

From Kinne and Cooley's " Shelter and Clothing," 
by kind permission. 




Fig. 44. — Cotton fibers magnified. Fig. 45. — Flax fibers magnified. 

From Kinne and Cooley's " Shelter and Clothing," From Kinne and Cooley's " Shelter and Clothing," 
by kind permission. by kind permission. 



TEXTILE FIBERS OF ANIMAL ORIGIN 219 

Experiment 124. 

Materials : 
Silk fibers. 
Wool. 

Human hair. 
Cat's hair. 
Apparatus : 

Microscope and slides. 
Examine the fibers, noting points of similarity among the various 
hair fibers and differences of these from the silk. Observe partic- 
ularly the scaly surface of the hair fibers. Is there any noticeable 
difference between wool and the coarser hair fibers in regard to 
(a) diameter, (b) appearance of the scales ? 

Wool 

A hair fiber comprises three distinct portions : (1) the 
medulla, a cellular marrow, which frequently contains the 
pigment to which the wool owes its color; (2) the fibrous 
cortical tissue, to which the fiber owes most of its strength 
and elasticity; (3) the epidermis of horny scales, consisting 
of flattened cells, overlapping one another like shingles. 

The characteristics which distinguish wool from other hair 
fiber are its fineness, its softness, and the abundance of its 
scales or serrations. To these scales is due the characteristic 
" felting " property of wool ; that is to say, the tendency of 
the fibers to mat together, and also the tendency of woolen 
goods to shrink, the scales catching upon one another and 
so preventing the fibers returning to their original position. 

The length and fineness of wool depend chiefly upon the breed 
of sheep producing it, but these qualities, as well as the strength 
and luster, are influenced also by the climate in which the sheep 
are grown, by the nature of the soil providing the pasture, and by 
the condition of the animals' health. Ordinarily, the length of 
the fibers is between 1 and 8 inches and the diameter between 3M0 
and 3^ inch. The quality of the wool varies not only in different 
fleeces, but also in the different parts of the same fleece, the wool of 
the shoulders and sides excelling in length, strength, and uniformity, 



2 20 ELEMENTARY HOUSEHOLD CHEMISTRY 

while that from the upper parts of the legs is coarse and that from 
the head, chest, and lower parts of the legs is likely to be coarse, 
stiff, and dirty. The uses of the wool depend upon its quality, 
which in turn depends upon such physical properties as the length, 
diameter, strength, elasticity, and glossiness of the fibers. 

Only the longer and brighter fibers, for instance, are suitable 
for the manufacture of worsteds. The wool manufacturer grades 
and sorts his wool and uses the different kinds for the manufacture 
of different classes of goods. 

Raw wool contains a large proportion of impurities. In 
some merino wools these impurities constitute as much as 
70 per cent of the total dry weight of the fleece. The im- 
purities consist of : 

(a) Wool grease, a fatty substance, which serves as a protective 
covering to the fibers. 

(b) Suint, that is, dried perspiration, consisting chiefly of potas- 
sium soaps. 

(c) Vegetable matter, such as burrs, straw, and vegetable fibers 
from sacks and twine. 

(d) Mineral matter, such as clay. 

Unwashed wool contains from 4 to 24 per cent of moisture; 
from 12 to 47 per cent of yolk (grease and suint) ; from 3 to 24 
per cent of dirt ; and from 15 to 72 per cent of true wool fiber. 

Wool grease, the chief constituent of which is an alcohol, called 
cholesterol, is the source of a product known as lanolin. Lanolin 
has remarkable capacity for forming emulsions with water and 
aqueous solutions, and is readily absorbed by the skin. On this 
account it is used in many pharmaceutical ointments and cosmetics. 

The impurities are removed from the wool by " scouring," 
that is, washing with soap and an alkali. Only the milder 
alkalies, such as the carbonates of potassium and sodium, 
ammonia or borax, may be used, not the caustic alkalies. 
By this treatment the soaps in the wool are dissolved, the 
fats are emulsified and removed from the wool fibers, and the 
earthy matters are thereby loosened and washed out. Much 
of the vegetable matter, however, remains in the wool and 
is removed by subsequent treatment. In the worsted pro- 



TEXTILE FIBERS OF ANIMAL ORIGIN 2 21 

cess this subsequent treatment is simply a combing, which 
removes not only the vegetable matter, but also those wool 
fibers which are too short to be used in worsted yarns. In 
the manufacture of woolens, where these shorter wool fibers 
are used, the vegetable matter is removed by a chemical 
process known as carbonizing. 

Carbonizing. — The washed wool is treated with dilute 
sulphuric acid (sp. gr. 1.03) and then subjected to a temper- 
ature of 140 to 180 F. (60-80 C), at which temperature 
the vegetable matter is rendered brittle by the conversion of 
the cellulose into hydrocellulose. The brittle residue is then 
shaken out of the wool, and the sulphuric acid is neutralized 
with soda and washed out. 

With the exception of the bleaching and dyeing, which will 
receive consideration later (Chapters XLII and XLIII), the 
remaining operations of the woolen industry — the carding, 
spinning, weaving, and finishing — involve no chemistry, but 
are purely mechanical. 1 

Experiment 125. 

Material: 

Scoured wool or woolen yarn. 

Weigh the wool (about 5 grams) on a balance accurate in the 
second decimal place. Dry for one hour in a water oven. Remove 
from the oven, place in a corked test tube, the weight of which 
has previously been determined, and as soon as the wool is cool, 
weigh again. Reheat for half an hour, weigh again, and repeat 
until the wool ceases to lose weight. Calculate the percentage 
of moisture. The wool should be allowed to cool in dry air. If 
a desiccator — i.e. an apparatus in which air is kept dry by ex- 
posure to sulphuric acid or calcium chloride — is at hand, the wool 
may be placed in it. 

Dry wool absorbs moisture from the air. Substances 
which do this are said to be hygroscopic. Dry wool is capable 
of taking up an average of 16 per cent of its own weight of 

1 For a description of these processes the reader is referred to Woolman and 
McGowan's "Textiles." (Seep. 228.) 



22 2 ELEMENTARY HOUSEHOLD CHEMISTRY 

water from ordinary air, while cotton absorbs only 8 or 8j 
per cent of its weight. The amount of hygroscopic moisture 
in wool at any given time depends upon the humidity of the 
atmosphere to which it has been exposed. 

In addition to the hygroscopic water, which is condensed 
on the surface of the fibers, wool contains some water chemi- 
cally combined with the protein compounds. Such water 
is known as " water of hydration." When in the manu- 
facture or subsequent treatment of woolen goods the water 
of hydration is driven off by overheating, the luster and 
strength of the fibers are irrecoverably lost. In pressing 
wool goods, therefore, care must be taken to avoid subjecting 
them to dry heat. 

Experiment 126. — Action of Acids. 

Material : 

White woolen yarn. 

Treat wool with (a) dilute sulphuric acid, (b) concentrated 
sulphuric acid, (c) dilute hydrochloric acid, (d) concentrated hydro- 
chloric acid, (e) concentrated nitric acid. If no action occurs in 
the cold, heat the acid. Which of the acids affects wool? Can 
you account for the effect of the nitric acid ? Neutralize the nitric 
acid solution with ammonia and note effect on color. 

Experiment 127. — Action of Alkalies. 

Treat white wool yarn with (a) sodium hydroxide solution, 
cold (allow to stand several hours) ; (b) sodium hydroxide, 
boiling ; (c) sodium carbonate, boiling ; (d) borax, boiling ; 
(e) ammonia. 

Where the yarn is not destroyed, pour off the reagent, rinse 
with water, and compare the strength of the treated yarn with 
that of a piece of the same yarn, untreated. 

Wool is not affected by dilute acids, but is very sensitive 
to alkalies, which, it will be remembered, readily attack 
most proteins. Soap containing free alkali should therefore 
be avoided in washing woolen goods. The free alkali dis- 
solves off the scales and renders the fibers hard and weak. 



TEXTILE FIBERS OF ANIMAL ORIGIN 223 

Soda (sodium carbonate), if free from caustic soda, is less 
harmful than soap containing caustic soda (free alkali). 
But soda is not without a certain amount of effect. Am- 
monia, borax, and neutral soap are permissible alkalies for 
the washing of woolen goods. 

Silk 

Experiment 128. 

Material : 

Silk. 
Apparatus : 

Microscope. 
Examine silk fibers under the microscope, comparing them with 
wool and hair fibers, as regards fineness and structure. 

Silk is obtained from the cocoons of a species of cater- 
pillar, which feeds upon the leaves of the mulberry tree. In 
making silk the silkworm secretes a viscous liquid, fibroin, 
in. two glands in its body, and forces this liquid through two 
minute channels in its head into a single exit tube. Two 
other glands deliver into the same tube a cementing fluid, 
known as sericin. As it emerges from the head of the worm 
the fibroin coagulates, thus forming a double thread cemented 
with sericin. 

Besides the silkworm proper there are other kinds of cater- 
pillars which produce silk. Since these latter worms are not 
cultivated by man, as are the mulberry silkworms, their products 
are known as wild silks. The best-known wild silk is tussah (or 
tussur) silk used in the manufacture of pongee. The wild silk 
fibers are coarser and hence stronger, but more broken than those 
of the mulberry silkworm. They are also commonly dark in 
color and hard to bleach. Wild silks find use in the manufacture 
of pile fabrics, such as velvet, plush, and imitation sealskin. 

The true silk fiber is notable for its great length and ex- 
treme fineness. The cocoon threads are only .0005 to .0007 



224 ELEMENTARY HOUSEHOLD CHEMISTRY 

inch in diameter (1430 to 2000 threads in the inch), but the 
length may be as much as 1300 to 1400 yards. Silk is also 
distinguished by its high luster and by its great strength and 
elasticity. 

About 75 per cent of the weight of the raw silk is fibroin, 
the fiber proper, and 25 per cent the cementing substance, 
sericin, also known as silk gum or silk glue. Both fibroin 
and sericin, although sulphur-free, behave like, and are 
classed as, proteins. Sericin, however, is soluble in hot 
water and forms a jelly on cooling. In this respect it closely 
resembles gelatin, hence the name " silk gelatin " sometimes 
applied to it. In the manufacture of silk more or less of the 
sericin is removed by treatment with hot soap solution, the 
process being known as boiling of, stripping, or degumming. 

Ecru silk is silk which has lost 2 to 5 per cent of its total weight, 
i.e. Yt to -J- of its sericin, in boiling off. 

Souple silk is that which has lost 12 to 14 per cent of its weight, 
i.e. about half its sericin. 

Boiled-of silk is that which has lost 22 to 25 per cent of its 
weight, i.e. practically all its sericin. 

Silk is, like wool, a hygroscopic substance. Under fa- 
vorable atmospheric conditions raw silk will absorb as much 
as 30 per cent of its weight of moisture without appearing 
wet. Boiled-off silk is, however, much less hygroscopic. 
Ordinarily, air-dry silk contains about 10 to 12 per cent of 
moisture, and it is the custom in the trade to buy and sell 
silk on the basis of its perfectly dry weight plus 1 1 per cent ; 
in other words the quantity of silk which when perfectly 
dried weighs 100 pounds is sold as in pounds of silk. 

Experiment 129. 

Weigh about 5 grams silk. Dry in oven at ioo° C. to constant 
weight, as in Experiment 125. What would be the legal weight 
of this piece of silk ? 



TEXTILE FIBERS OF ANIMAL ORIGIN 225 

Experiment 130. — Action of Acids. 

Material : 

White silk thread. 

Treat silk thread with acids, as in Experiment 126, and either 
compare with the results obtained on wool in that experiment or 
make the experiments on wool and silk in parallel. Compare the 
rates of solution in concentrated nitric acid. Note particularly the 
difference in the effect of cold concentrated hydrochloric acid on 
the two materials. The violet coloration produced by the action 
of concentrated hydrochloric acid on boiling or long standing is 
one of the characteristic reactions of proteins. 

Experiment 131. — Action of Alkalies. 

Make experiments on silk parallel to those of Experiment 127. 
Which of the two materials is the more susceptible to the action 
of alkalies? Which to the action of acids? 

Experiment 132. — Action of Basic Zinc Chloride (Eisner's 
Reagent l ). 

Heat Eisner's reagent to boiling. Tie a silk thread on to a glass 
rod and dip into the hot liquid. Make the same experiment with 
a piece of woolen yarn. 

The above experiments suggest methods of quantitatively 
determining the proportion of silk in a mixed fabric of wool 
and silk. The silk may be dissolved out with either con- 
centrated hydrochloric acid or boiling basic zinc chloride, 
and the undissolved residue of wool washed, dried, and 
weighed. 

The Weighting of Silk 

Silk absorbs and combines with the tannins or tannic 
acids, — organic substances contained in various plants and 
used in tanning leather, — and the tannins, in turn, react with 
iron salts, giving dark-colored dye products. By successively 
treating silk with an iron salt and a tannin the weight of the 

1 Dissolve 500 grams zinc chloride and 20 grams zinc oxide in 425 cc. water, 
warming till clear. The liquid becomes turbid on standing in the cold, but 
clears again on heating. 

Q 



2 26 ELEMENTARY HOUSEHOLD CHEMISTRY 

fibers can be greatly increased. Sometimes potassium or 
sodium ferrocyanide is used in place of, or in addition to, 
the tannin. Ferrocyanides and ferric salts Teact together to 
form Prussian blue, an insoluble substance which precipi- 
tates in the fibers. Thus : 

Ferric . Sodium Ferric , Sodium 

nitrate ferrocyanide ferrocyanide nitrate 

(Prussian blue) 

Experiment 133. 

Materials : 

Tannin of gallnuts. 
Cutch (catechu). 

Infuse 10 grams of each of the tannin materials separately with 
100 cc. water. Filter. 

In test tubes mix solutions of : (a) Ferric chloride and gallnut 
tannin (gallotannic acid), (b) Ferric chloride and cutch infusion 
(containing catechutannic acid), (c) Ferric chloride and potassium 
ferrocyanide. 

Dilute the dark products until you can see through the liquid. 
In which instance is a precipitate formed ? 

Experiment 134. 

Materials : 
Cutch. 

Ferric nitrate or ferric acetate. 
Piece of woven ecru silk. 

Infuse 10 grams cutch with 100 cc. water. Dissolve 10 grams 
ferric nitrate in 100 cc. water. Weigh the piece of silk (1 to 2 
grams). Heat the ferric nitrate solution to 70-80 C. and immerse 
the silk in it for 10 minutes. Squeeze out, transfer to the cutch 
bath, and heat to boiling. Repeat the treatment with ferric 
nitrate and that with cutch several times. Rinse with hot water, 
dry, and weigh. If heat is applied in drying, allow the silk to 
stand in the room for a few hours before weighing. Calculate 
the percentage gain in weight. 

A few crystals of stannous chloride added to the cutch bath 
may produce a greater gain of weight. 

Weighting with iron compounds is only practicable where 
the silk is to be dyed black or a dark color. For white and 



TEXTILE FIBERS OF ANIMAL ORIGIN 227 

light-colored silks soluble substances such as sugar, glucose, 
and magnesium chloride were formerly and are still some- 
times used, but the most successful weighting materials are 
insoluble compounds of tin. Tin silico-phosphate is one of 
the most common of these weighting materials for light- 
colored silk. It is obtained by treating the goods first with 
stannic chloride, then with sodium phosphate, and finally 
with sodium silicate. 

Experiment 135. 

Materials : 
Ecru silk. 

Stannic chloride crystals (or anhydrous stannic chloride). 
Disodium phosphate crystals. 
Sodium silicate (or water-glass solution). 

Dissolve 40 grams stannic chloride crystals (SnCU . 5 H 2 0) or 
30 grams (13 cc.) anhydrous stannic chloride in 70 cc. of water. 
Dissolve 13 grams sodium phosphate crystals (Na2HP04 . 12 H 2 0) 
in 87 cc. water. Dilute water-glass solution to a specific gravity 
of 1.04. 

Weigh a piece of ecru silk (1 or 2 grams). Place it in the stan- 
nic chloride solution and let stand one hour. Heat the sodium 
phosphate solution and the sodium silicate solution to 6o° C. 
(140 F.). Remove the silk from the stannic chloride, rinse it 
with water, and immerse in the sodium phosphate solution for 10 
minutes, then in the sodium silicate for the same length of time. 
Rinse, dry, and weigh. 

The process may be repeated five or six times, the weight in- 
creasing with each treatment. 

Compare the weighted silk with an untreated piece of the same 
goods, noting particularly the relative strength of the fibers. 

Burn a thread of heavily weighted and a thread of unweighted 
silk. What differences of behavior are observed? 

Silk experts maintain that moderate weighting — up to 
about 25 per cent of the weight of the boiled-off silk — is not 
injurious, but rather improves the wearing quality of the silk. 
Indeed, the term " pure silk " is used in the trade to designate 
a silk which has been weighted just sufficiently to compensate 



2 28 ELEMENTARY HOUSEHOLD CHEMISTRY 

for the loss of weight sustained in boiling off. It is generally 
agreed, however, that excessive weighting is very injurious. 
Goods weighted with tin compounds are -especially liable 
to deterioration on exposure to air and light. It is thought 
that this may be due to the hydrolytic effect of moisture on 
the stannic chloride retained in the fibers. Such hydrolysis 
would liberate hydrochloric acid, which, as we have seen, has 
a solvent action on silk. Proceeding on this assumption, some 
manufacturers treat tin-weighted goods with mildly basic 
organic compounds, and this is said to mitigate the evil to 
some extent at least. 

The most satisfactory methods of estimating the amount of 
weighting in silk are : 

(i) Treatment with dilute hydrofluoric acid, which dissolves 
the weighting without affecting the silk. 

(2) Determination of the amount of nitrogen in the material 
after first freeing it from nitrogenous weighting materials, such 
as Prussian blue, ammonium phosphate, glue, and gelatin. Since 
pure boiled-off silk containing 11 per cent of moisture contains 
17.6 per cent of nitrogen, every gram of nitrogen found in the 
weighted goods represents 100 4-17.6 = 5.68 grams of air-dry silk. 
The difference between the original air-dry weight and the esti- 
mated air-dry weight of real silk represents the weight of the 
filling material. 

(3) Burning the goods and weighing the ash. This is a simple 
method which gives good results with light-colored goods. Un- 
weighted silk leaves less than 1 per cent of its weight of ash. 
Silk legitimately weighted leaves not over 25 per cent. Silks 
yielding more than 25 per cent of ash are overweighted. In the 
case of black goods the amount of weighting may considerably 
exceed the amount of ash, since some of the weighting substances, 
e.g. tannin, are combustible. 

For an account of the silk industry and of the properties of silk fibers and 
fabrics which should influence their selection and use, reference may be made to 
Woolman and McGowan's "Textiles: A Handbook for the Student and the 
Consumer" (New York, 1913). 



CHAPTER XLI 

TEXTILE FIBERS OF VEGETABLE ORIGIN. COT- 
TON, LINEN, AND ARTIFICIAL SILK 

Vegetable fibers are of great variety if we include such 
materials as are used in the manufacture of furniture and 
floor coverings — twigs, canes, rushes, grasses, leaf fibers 
(e.g. manila, sisal), etc. Leaving these coarse materials 
out of consideration, the natural vegetable fibers resolve 
themselves into two classes : 

(i) Seed hairs, of which cotton is the only important 
example. 

(2) Bast fibers, including linen, ramie, jute, and hemp. 

Artificial silks (lustracelluloses) are artificial fibers made 
from vegetable materials. 

All these materials are carbohydrate in composition and 
all belong to that class of carbohydrates known as celluloses. 
Between the cellulose of cotton and that of linen there is 
little, if any, difference. 

Wood-pulp paper and jute consist of lignocellulose, a dis- 
tinctly different substance from true cellulose. Hemp prob- 
ably contains both these kinds of cellulose. 

Cotton 

Cotton fibers are the seed hairs of several varieties of the 
cotton plant (genus, Gossypium), most species of which grow 
as shrubs in warm climates. 

The seed hairs are inclosed with the seed in a sort of pod, 
known as a boll. The bolls are harvested when they burst 
open, exposing the ripe cotton. 

229 



230 ELEMENTARY HOUSEHOLD CHEMISTRY 

Experiment 136. 

Examine cotton fibers under the microscope at a magnifica- 
tion of about 150 to 300. Note the ribbon-like form and the 
characteristic twist. Under a higher magnification (about 700) 
note the inner canal of the fiber. 

Cotton fibers (or staple, as they are technically termed) 
of American growth vary in length from § inch in Texas to 
i| inches in Uplands, and in diameter from 2 o 1 oo to yoVo inch, 
the longer fibers having the smaller diameters. 

They are, accordingly, comparable in diameter with silk 
and fine wool, but much shorter than either silk, wool, or 
linen fibers. (See pp. 223, 219 and 236). Sea Island cotton, 
originally grown in the West Indies, and Egyptian cotton, 
which has been developed from Sea Island stock, have a 
longer staple and are finer than that from the American 
mainland. It is this finer variety of cotton which is em- 
ployed in the manufacture of mercerized lawns. 

Cotton fibers consist of a single cell, the structure of which 
is represented in Figure 44. During growth the interior 
tube {lumen) is filled with a liquid, and the fiber is cylindrical. 
On ripening, the liquid withdraws and the fiber flattens irregu- 
larly into a twisted ribbon. The twist is not only a valu- 
able mark of identification of cotton fibers, but is also of 
great practical importance in facilitating spinning. As a 
means of interknitting the fibers it plays a part similar to 
that played by the epidermal scales in wool. Raw cotton 
fibers have 300 to 500 twists per inch. 

The raw fiber is mixed with, and attached to, the cotton 
seed. The seed is removed by mechanical processes {gin- 
ning) — not, however, without some injury to the fibers. 
A waxy coating also covers the fiber. The quantity of wax 
is small — usually between 0.3 and 0.5 per cent. After 
the cotton is spun, this wax is removed by boiling the cotton 
6 or 8 hours in a dilute (1 per cent) solution of caustic soda 
under slight pressure. The bleaching of cotton is not under- 
taken until the wax has been removed. 



TEXTILE FIBERS OF VEGETABLE ORIGIN 231 

Chemical Behavior 

Boiled-off cotton is practically pure cellulose. To most 
reagents cellulose is much more resistant than the protein 
substances which constitute the animal fibers. 

Experiment 137. — Action of Acids. 

Treat wisps of absorbent cotton in test tubes with (a) concen- 
trated sulphuric acid, (b) concentrated hydrochloric acid, (c) con- 
centrated nitric acid, allowing it to stand in the cold for 5 or 10 
minutes. Afterwards heat tubes (b) and (c). Cool tube (c) and 
neutralize the nitric acid with ammonia. Record the effect of each 
of the three acids, and compare with the effects on wool and silk. 
How could the results be utilized to distinguish (1) cotton from 
wool and silk, (2) cotton and wool from silk? 

Experiment 138. — Action of Acids. 

Immerse two pieces of woven cotton goods for a few minutes 
in dilute sulphuric acid and two similar pieces in a saturated 
solution of oxalic acid. Without rinsing, immerse one piece from 
each acid in ammonia. Dry the four pieces on watch glasses in 
a water oven at 60-80 C. (140 to 180 F.). Note how the acids 
have affected the strength of the fabric. Is this effect produced 
by the cold solutions of the acids ? (Compare the pieces in which 
the acid was neutralized by the ammonia before drying.) 

It is sometimes stated that the injury produced by organic 
acids, such as oxalic and tartaric, is purely mechanical, due to 
the crystallizing of the acids in the fibers. Do your results sup- 
port this view? Can you suggest other methods of testing this 
theory ? 

When acids are accidentally spilled upon cotton goods, what 
means should be taken to prevent injury to the fabrics ? 

When strong alkalies are spilled upon cotton goods, how are 
they best neutralized? What acids may be used and what pre- 
cautions should be observed in their use ? 

Explain the use of dilute sulphuric acid in the purification of 
wool from burrs and other vegetable matter. (See p. 221.) 

Cellulose proper — e.g. that of boiled-off cotton and 
bleached linen — dissolves readily in the cold in concen- 



232 ELEMENTARY HOUSEHOLD CHEMISTRY 

trated sulphuric acid and in strong solutions of certain salts 
in concentrated hydrochloric acid. Among such salts are 
mercuric chloride and zinc chloride. A hot concentrated 
solution of the latter salt (being much hydrolyzed) will dis- 
solve cellulose without the addition of any hydrochloric acid. 
Before going into solution in any of these reagents the 
fibers swell and soften, probably on account of the combining 
of water with the cellulose. This swelling is utilized in the 
manufacture of parchment paper and in one of the processes 
of waterproofing cotton goods. 

Experiment 139. 

Pour 20 cc. concentrated sulphuric acid into 10 cc. water in a 
beaker or dish. Allow to cool to room temperature. Provide another 
beaker or dish of water. Dip a strip of filter paper into the acid 
for about five seconds, then transfer it quickly to the water. Wash 
thoroughly. Compare the appearance and strength of the treated 
paper with that of wet untreated filter paper. Treat each with 
iodine solution. 

Cellulose, being carbohydrate, has the characteristics of 
an alcohol (with many — OH groups). It is, therefore, ca- 
pable of reacting with acids to form esters and, having many 
— OH groups, it can form several esters with one acid. The 
nitrates of cellulose are made commercially, not only for use 
as explosives, but also for the manufacture of collodion and 
artificial silk. Cellulose is nitrated by treatment with a 
mixture of nitric acid and concentrated sulphuric acid. 
Cellulose nitrates are commonly called nitrocelluloses. 

Experiment 140. 

Mix 20 cc. concentrated sulphuric acid and 10 cc. concentrated 
nitric acid. Allow to cool to room temperature. Immerse absorbent 
cotton in this mixture for about one minute. Wash thoroughly with 
cold water, wring out, and allow to dry on filter paper. Set a piece 
of the dry product and a piece of the untreated cotton on fire and 
compare the rapidity with which they burn. 



TEXTILE FIBERS OF VEGETABLE ORIGIN 233 

This product is a "nitrocellulose" (guncotton or pyroxylin). 
Shake a portion of the dry guncotton with a mixture of alcohol 
and ether. (A residue of unchanged cellulose will remain.) 
The clear liquid (a solution of nitrocellulose in ether and alcohol) 
is collodion. Pour a little of it on a glass plate and allow to 
evaporate. (Keep flames away.) Surgeons sometimes use 
collodion to form a coating over wounds. Such a coating is 
adherent, flexible, and impermeable to air and water. 

Experiment 141. 

Material : 

Collodion prepared in the preceding experiment. 

Pour a little of the collodion solution on water in a test tube. 
Note that it forms a clear layer above the water. Shake the tube. 
The precipitate is nitrocellulose. 

Experiment 142. — Action of Alkalies. 

Boil a piece of cotton yarn or woven cotton goods for a few 
minutes with dilute sodium hydroxide solution. Wash, neu- 
tralize the alkali by dipping into water containing a little acetic 
acid, and wash again. Compare the strength of the goods with 
that of untreated cotton of the same kind. Contrast the effect 
of alkalies on cotton with that on wool and silk. How could this 
difference be utilized in the analysis of mixed goods? 

Experiment 143. — Action of Alkalies. 

Cover a piece of cotton with a strong solution of caustic soda 
(30 per cent) or caustic potash (50 per cent) and allow to stand 
10 or 15 minutes. Remove the cotton, wash in a stream of cold 
water, dip into dilute acetic acid, and wash again. Note the ap- 
pearance of the cotton, comparing it with that of untreated cotton. 



Mercerization 

Mercerization is a process to which cotton is sometimes 
subjected to increase its luster, its strength and wearing 
qualities, and its capacity for taking dyes. The cotton is 
stretched on a frame and subjected to the action of a strong 
cold solution of sodium hydroxide (about 30 per cent NaOH), 
after which it is washed with water. The effect of the strong 



234 ELEMENTARY HOUSEHOLD CHEMISTRY 

solution of alkali on unstretched cotton is to swell and shorten 
the fiber, causing shrinkage of the goods. When the goods 
are stretched, the shrinkage is overcome or^ prevented, but 
the fibers are untwisted and acquire a high luster. It is 
supposed that the alkali hydroxide combines chemically 
with the cellulose, and that, on washing, the metal of the 
alkali is replaced by hydrogen, leaving hydrated cellulose, i.e. 
a compound of cellulose with water. 

The process takes its name from John Mercer, who in 1844 
first observed the action of concentrated solutions of the caustic 
alkalies on cotton, and in 1850 took out a patent on the process. 
The stretching of the fabric to prevent shrinkage and produce a 
high luster was a later development introduced by Lowe in 1889. 
It is only since this later discovery that the process has become 
commercially successful. Long-stapled cottons (Egyptian and 
Sea Island), which are naturally more glossy than the commoner 
short-stapled varieties, are preferred in the manufacture of mer- 
cerized goods. 

Sizing, or Dressing of Cotton Goods 

Cotton goods are commonly sized or otherwise finished 
to give an attractive (sometimes a deceptively attractive) 
appearance. In the trade, the term sizing is commonly 
used to designate the process of applying dressing materials 
to the warps, while the application of the same materials 
to the woven fabric is termed finishing. Among the mate- 
rials used for various purposes are : 

{a) Stiffening agents : starch, flour, dextrin, glue, gelatin, gums. 

(b) Softening agents : fats, waxes, soaps. 

(c) Filling and weighting agents : aluminium silicate {China 
clay), calcium sulphate {gypsum), magnesium silicate {talc), calcium 
carbonate {whiting), barium sulphate {blanc fixe). 

{d) Hygroscopic agents — which both add weight and soften : 
magnesium chloride, calcium chloride, glycerin. 

(e) Preservative agents — to prevent the growth of mildew and 
other organisms : zinc chloride, carbolic acid, cresols, salicylic acid, 
boric acid. 



TEXTILE FIBERS OF VEGETABLE ORIGIN 235 

The basis of the size is practically always starch. This 
can be removed by boiling with dilute acid, which hydrolyzes 
it and thus loosens the filling materials. Subsequent treat- 
ment with dilute alkali removes the fats and waxes. 

Experiment 144. — Determination of Dressing Materials. 

Material : 

White cotton goods, unwashed. 

Wet a small portion of the goods and test with iodine solution 
for starch. Prepare a 3 per cent solution of hydrochloric acid 
(by diluting 400 cc. of the reagent dilute hydrochloric acid to 
1 liter) and a 1 per cent solution of sodium carbonate (by diluting 
100 cc. of the reagent solution to 1 liter). 

Weigh a piece of the dry goods (2 to 5 grams). Boil 10 or 15 
minutes in the 3 per cent hydrochloric acid. Cool, rinse, and test 
for starch. If present, boil again with the acid. Rinse and boil 5 
minutes in 1 per cent sodium carbonate solution. Rinse thoroughly, 
dry, allow to stand in the air of the room for 2 or 3 hours, and weigh. 
The difference between the initial and the final weight is the weight 
of the dressing materials. 



Linen 

Linen is a bast {i.e. inner bark) fiber obtained from flax 
stalks. These are cut or pulled, while still somewhat green, 
stripped of seeds and leaves by a machine, and then subjected 
to a fermentation known as " retting " — i.e. rotting. Ret- 
ting is conducted either in water (tanks or running streams) 
or by exposure to the weather (dew retting) or both. Its 
effect is to convert the substances holding the fibers together 
into soluble compounds which are washed out. Thus an 
enzyme (pectinase) secreted by certain bacteria acts upon 
the calcium pectate between the cells, converting it into 
pectin, sugars and soluble calcium salts. The remaining 
impurities — bark, woody tissue, etc. — are removed by me- 
chanical processes, and the fiber then undergoes much the 
same treatment as cotton. 



236 ELEMENTARY HOUSEHOLD CHEMISTRY 

Experiment 145. 

Examine unbleached and bleached linen fibers under the mi- 
croscope, comparing them with cotton fibers Moisten with a 

dilute solution of iodine and examine again. 

Note particularly the absence of twist and the presence of cross- 
markings at the junctions of the cells — similar to the " knots " 
in straw. 

Linen fibers are from 8 inches to 5 feet long, averaging 20 
inches, and from -gwo to -q^q inch in diameter, averaging 
about t-^oq- inch. They are thus much longer, and on the 
average a little coarser than cotton fibers. Under the mi- 
croscope the flax fiber appears as a long, straight, cylindrical 
tube with a narrow lumen, often appearing as a mere black 
streak. There are cross markings on the cylinder, and nodes 
resembling the knots on straw. These markings, which 
are emphasized by treatment with iodine, constitute one of 
the best means of identifying linen fibers. The natural ends 
of the flax fibers are narrow and pointed. 

The flax fiber is not, like the cotton fiber, a single cell, but 
consists of a bundle of cells, averaging about 1 inch in length 
and ttVo mcri in diameter at the middle. The fiber of flax 
is more porous than that of cotton, and the following very 
good test, particularly for bleached goods, is based upon this 
property. 

Experiment 146. — Oil Test for Linen. 

Free the sample from dressing by boiling in 3 per cent hydro- 
chloric (or 5 per cent oxalic) acid. Treat with 1 per cent sodium 
carbonate solution, rinse with distilled water, and dry. Fringe 
out the goods on two adjacent edges, so as to expose ends of warp 
and weft threads. Moisten the piece thoroughly with olive oil 
or glycerin. Press between filter papers and place against a dark 
background. The linen fibers or threads appear translucent, 
the cotton fibers remain opaque white. 

The linen fiber is stronger, but harder and less resilient 
(elastic) than cotton. It is also a better conductor of heat 



TEXTILE FIBERS OF VEGETABLE ORIGIN 237 

and therefore feels cooler to the touch. Experts can some- 
times distinguish cotton goods from linen by feeling them. 
Dressings, however, may interfere here. 

Bleached linen, like bleached cotton, is almost pure cellu- 
lose. Unbleached flax fiber, however, contains from 0.5 to 

2 per cent of a wax-like substance and 2.5 to 10 per cent of 
intercellular substance and pectins. Unbleached or incom- 
pletely bleached linen often shows a noticeable difference 
from cotton on treatment with staining materials. Many 
distinguishing tests have been based upon this fact. 

Experiment 147. 

Materials: 

Rosolic acid solution (0.5 gram in 50 cc. water and 50 cc. 

alcohol) . 
Samples of pure cotton and pure linen goods. 
Sample with linen warp and cotton weft. 
Warm the mixture. Fringe out the samples on two adjacent 
edges and immerse in the solution for five minutes. Remove, 
wash with water, with dilute ammonia, and again with water, 
Dip into concentrated sodium hydroxide solution ; again wash 
thoroughly, and allow to dry. Note which of the materials is 
permanently reddened. 

Experiment 148. 

Materials : 

Cyanin solution (0.1 gram in 50 cc. alcohol and 50 cc. 
water) . 

The same fabrics as in Experiment 147. 
Fringe out the samples, warm them in the cyanin solution for 

3 minutes. Wash. Lay in water acidulated with sulphuric acid, 
then treat with dilute ammonia. 

One of the most useful tests for distinguishing cotton 
from, and detecting cotton in, linen goods is treatment with 
cold concentrated sulphuric acid. This test is most success- 
ful with coarse-woven goods, such as towelings, but by vary- 
ing the time of immersion may be made to succeed even with 
a handkerchief weave. 



238 ELEMENTARY HOUSEHOLD CHEMISTRY 

Experiment 149. 

Free the material completely from dressing by boiling with 
3 per cent hydrochloric or 5 per cent oxalic acid, treating with 
1 per cent sodium carbonate solution and rinsing with distilled 
water. Dry the goods. Immerse in concentrated sulphuric 
acid from 1^ to 2 minutes, according to the texture of the material. 
Remove, wash thoroughly with water, then with dilute ammonia. 
Cotton fibers are destroyed, linen fibers remain. 

Linen warp threads in goods with cotton weft can be retained 
in position in this test by tying the goods to microscope slides with 
strong linen thread. 

Although linen is more resistant to sulphuric acid than 
cotton, it is less resistant to boiling alkaline solutions and to 
bleaching powder and other oxidizing agents. 

The dressing* materials applied to linen goods are similar 
to those used for cottons. The amount of hygroscopic mois- 
ture in linen is about the same as that in cotton, viz. 6 to 8 
per cent. 

Lustracellulose (" Artificial Silk ") 

" Artificial silk " fibers are made from cellulose (cotton or 
wood pulp) by dissolving it in a suitable solvent, forcing the 
solution through minute openings, and reconverting it into 
a solid form as it issues in fine streams. The threads thus 
produced resemble silk in structure, being formed by a 
process similar to that used by the silk worm. In size (both 
length and diameter) and in luster they approximate much 
more closely to silk fibers than do mercerized cotton fibers. 
Chemically they are not protein, like the fibroin of silk, but 
carbohydrate, viz. cellulose. From the chemical standpoint, 
therefore, the name lustracellulose is preferable to artificial 
silk. 

Attempts have been made to manufacture artificial protein 
fibers from gelatin and from casein. These processes, however, 
have not been commercially successful. 



TEXTILE FIBERS OF VEGETABLE ORIGIN 239 

The three leading processes of manufacturing artificial 
silk are : 

1 . That known from its inventor as the Chardonnet Process 
and from its intermediate products as the Pyroxylin or 
Collodion Process. The cellulose is converted into nitro- 
cellulose by treatment with nitric and sulphuric acids. (See 
Expt. 140, p. 232.) The nitrocellulose is dissolved in ether 
and alcohol and the resulting collodion forced through the 
narrow openings into a warm chamber. The alcohol and 
ether evaporating from the threads are recovered and used 
over and over again. The nitrocellulose fibers are recon- 
verted into cellulose (" denitrated ") by immersion in a solu- 
tion of ammonium sulphide. 

The Chardonnet Process, although expensive, is still in use 
in France. 

2. The Cuprate or Cuprammonium Process. The cellu- 
lose is dissolved in an ammoniacal solution of copper hy- 
droxide and the threads delivered into an acid, which re- 
precipitates the cellulose. This process is used principally in 
Germany. 

3. The Viscose Process. The cellulose (usually wood 
pulp) is treated with a strong caustic soda solution such as is 
used in mercerizing. The alkali cellulose thus obtained is 
treated with carbon disulphide. Combination occurs with 
the production of a compound soluble in water, but insoluble 
in alcohol and in brine. This compound is called " viscose " 
on account of the extraordinary viscosity of its solution in 
water. The viscous solution is forced through fine openings 
into a concentrated solution of sodium chloride or ammonium 
chloride which precipitates the viscose in threads. The 
latter is then decomposed by heat into cellulose and water- 
soluble products, which latter are washed out. 

The chemical reactions involved in the Pyroxylin Process 
are illustrated by Experiments 140 and 141 above. 



240 ELEMENTARY HOUSEHOLD CHEMISTRY 

Experiment 150. — The Cuprate Process. 

Dilute 10 cc. copper sulphate solution to about 150 cc. in 
a beaker. Add a few drops ammonium chloride solution, and, 
without heating, add sodium hydroxide solution until the precipi- 
tate formed just begins to darken in color. Allow to settle, 
filter, and wash the precipitate with cold water. (What is this 
precipitate ?) Remove the precipitate from the filter paper, place 
it in a dish, cover with ammonium hydroxide, and stir. Pour off 
the clear solution into a test tube, add some absorbent cotton, and 
shake. Pour a little of the solution thus obtained into dilute acid 
in a test tube. The precipitate is the regenerated cellulose. 

Experiment 151. — The Viscose Process. 

Cover a little absorbent cotton in a beaker with 30 per cent 
sodium hydroxide (or 50 per cent potassium hydroxide) solution 
and allow to stand for an hour or longer. Remove the alkali- 
cellulose from the liquid by use of a glass rod. (Better results 
will be obtained if the moist mass is now placed in a stoppered 
bottle or test tube and allowed to stand two or three days. This, 
however, is not essential to the success of the experiment.) 

Cover the moist mass with carbon disulphide, shake vigorously, 
and allow to stand until quite yellow (about 3 hours). Pour off 
the excess of carbon disulphide, cover the product with water, 
and again allow to stand for an hour or more. Shake, and add 
enough additional water to give a thick brown liquid. This is 
the viscose solution. Pour portions of it into (a) alcohol, (b) a 
saturated solution of ammonium chloride. A portion may also 
be forced through a piece of glass tubing drawn to a capillary. 
Dip the capillary end of the tube under the surface of alcohol or 
saturated ammonium chloride solution and blow steadily into the 
tube. The viscose will precipitate in threads. 

Pour the main portion of viscose solution into a small, flat-bot- 
tomed dish (a crystallizing dish), cover it with alcohol, and allow 
to stand half an hour. Pour off the alcohol, being careful not to 
disturb the sediment of viscose. Rinse two or three times with 
alcohol, then heat on a water bath. The viscose is decomposed 
by the heat. Rinse the dry residue several times with water. 
This removes the other decomposition products, leaving the cel- 
lulose in the form of a film. 



TEXTILE FIBERS OF VEGETABLE ORIGIN 241 

Experiment 152. 

Materials : 
Artificial silk. 
True silk. 
Mercerized cotton. 
Ravel out threads of each. Could the mercerized cotton be 
recognized by the length of the fibers ? 

Break equal-sized threads of each, comparing the strength of 
the threads. 

Wet each thoroughly and again compare the strength of the 
threads. 

Burn a little of each and note odor. 
How can you distinguish : 

(a) Artificial silk from mercerized cotton. 

(b) Lustracellulose from silk. 

The following methods may be used for the quantitative 
analysis of mixtures of cotton and wool and of cotton and 
silk. 

Experiment 153. — Analysis of a Wool-cotton Fabric. 

Materials : 

Fabric containing wool and cotton. 
5 per cent solution of potassium hydroxide. 
1 per cent solution of hydrochloric acid. 
0.05 per cent solution of sodium carbonate. 
Weigh the sample. Remove the finishing materials by boiling 
30 minutes in 1 per cent hydrochloric acid, rinsing, and boiling 
thirty minutes in 0.05 per cent sodium carbonate. Wash thoroughly, 
air-dry, and weigh. The loss represents finishing materials. 
Dry to constant weight in a water oven. The loss represents 
moisture, and the residue is dry fiber. 

Boil for 20 minutes in 5 per cent caustic potash. Wash well, 
dry in the water oven to constant weight. Add 5 per cent to 
the weight of the residue, because the cotton is attacked to about 
that extent. The residue is the weight of dry cotton, the loss that 
of dry wool. 

Experiment 154. — Analysis of a Silk-cotton Fabric. 

Materials : 

Fabric of silk and cotton. 

Eisner's reagent (basic zinc chloride). 

R 



242 ELEMENTARY HOUSEHOLD CHEMISTRY 

Determine the quantities of finishing material and moisture as in 
Experiment 153. 

Immerse in the boiling basic zinc chloride solution for one 
minute. Wash thoroughly with 1 per cent hydrochloric acid, 
then with water ; dry and weigh. Add 1^ per cent to the weight 
of the residue. The result represents the amount of cotton. 

The silk may also be dissolved by immersion for 5 minutes at 
room temperature in Richardson's reagent (an ammoniacal solu- 
tion of nickel hydroxide) or for 15 minutes at 50 C. in Lowe's 
reagent (an alkaline solution of copper hydroxide and glycerol) . 

Richardson's reagent is prepared by dissolving 25 grams nickel 
sulphate in 500 cc. water, precipitating completely with sodium 
hydroxide, washing thoroughly by settling and decantation, 
dissolving in 125 cc. concentrated ammonia and making up to 
250 cc. 

Lowe's reagent is prepared by dissolving 25 grams copper 
sulphate in 250 cc. water, adding 12 cc. glycerol and just sufficient 
sodium hydroxide solution to redissolve the precipitate which 
forms at first. 

The methods of manufacturing cotton and linen fabrics and their properties 
in relation to selection and use are fully discussed by Woolman and McGowan in 
the work already referred to (p. 228). 



CHAPTER XLII 

BLEACHING AND BLUEING 

While a great many chemical compounds are white — e.g. 
sugar, salt, starch — there are many others that are char- 
acterized by certain colors. When such compounds undergo 
chemical change, their characteristic colors disappear and 
the colors of the products of the chemical change make their 
appearance. Indeed, a change of color is commonly accepted 
as an indication of chemical change. 

A change of color is only an indication, not a proof, that chem- 
ical change has taken place. The color of a solid substance may 
be materially altered by a change of physical condition. Thus 
large copper sulphate crystals appear dark blue, while small 
crystals are lighter blue ; cold zinc oxide is white, but hot zinc 
oxide yellow. 

To bleach a textile, whether for the purpose of removing the 
natural color of the fiber or to take out a stain or to remove 
a dye, what must be done is to convert the color-bearing com- 
pound or compounds into colorless products. The natural 
coloring matters of textile fibers, and practically all the dyes 
which are used upon textiles, are organic substances, i.e. car- 
bon compounds. There are two general methods of convert- 
ing organic coloring matters into colorless products : 

i. By Oxidation. — This may be accomplished by the 
action of free oxygen, especially under the influence of direct 
sunlight. The " grass bleaching " of linen is a familiar ex- 
ample. More rapid action can, as a rule, be attained by the 
use of an oxidizing agent, i.e. a compound which readily gives 
up oxygen to other substances. Among the oxidizing agents 
used in bleaching are calcium hypochlorite, sodium hypo- 
chlorite, hydrogen peroxide, and potassium permanganate. 

243 



244 ELEMENTARY HOUSEHOLD CHEMISTRY 

2. By Action of Sulphurous Acid, H 2 S0 3 . — Sulphurous 
acid is a reducing agent (see Expt. 98, p. 169), being readily 
oxidized to sulphuric acid, H2SO4. No doubt in many in- 
stances it bleaches by removing oxygen from the color- 
bearing compound. But it also has the power of combining 
with some kinds of organic substances, and its bleaching action 
may often be due to combination rather than to reduction. 
Its action is in many instances not fully understood. 

In the removal of the natural colors from textile fabrics 
the choice of a bleaching agent must be governed by its effect 
upon the fiber substance itself, as well as by its cost and its 
effectiveness in destroying the coloring matter. In house- 
hold bleaching, likewise, the effect of the bleaching agent 
upon the material to be bleached must be known and borne 
in mind. 

Hypochlorites 

The most active bleaching agent, and the cheapest except 
atmospheric oxygen, is bleaching powder. 

This is made by the combining of chlorine with lime, 
whence the alternative name, chloride of lime. It has the 
composition represented by the formula CaOC^, and when 
dissolved in water ionizes thus : 

CaOCl 2 = Ca ++ + Cl~ + OC1" 

The hypochlorite ions, OCl~, readily give up oxygen, 
especially in presence of acid, where they first unite with 
hydrogen ions, H + , to give the unstable hypochlorous acid, 
HCIO. Bleaching-powder solutions, therefore, especially 
when acidified, act as strong oxidizing agents. 

Experiment 155. — Bleaching Powder. 

Materials : 

Bleaching powder. 
Mortar and pestle. 
Cobalt nitrate solution (10 per cent). 



BLEACHING AND BLUEING 245 

Grind about 10 grams bleaching powder in a mortar, and gradually 
add about 5 grams of water so as to form a paste. Add an addi- 
tional 25 cc. water, mix thoroughly, and filter. Note the odor 
of the filtrate. Heat a portion of it and note whether the odor 
becomes stronger. Also note whether a precipitate forms. The 
odor is that of hypochlorous acid and the precipitate is calcium 
hydroxide. What effect do you infer that heat has on the hydrol- 
ysis of calcium hypochlorite ? 

To a portion of the filtrate add a few drops of cobalt nitrate 
solution, cover the test tube with the thumb for a minute or so, 
then test the evolving gas with a glowing splint. What is the gas? 
Is it pure? (Note odor.) The black precipitate, which is an 
oxide of cobalt, acts as a catalytic agent, causing rapid decomposi- 
tion of the hypochlorous acid. 

To a portion of the original nitrate add dilute hydrochloric acid. 
Note color and odor. These are due to chlorine, hydrochloric 
and hypochlorous acids reacting thus : 

HC1 + HCIO = HoO + Cl 2 

Experiment 156. — Bleaching Effect. 

Materials : 

Bleaching-powder solution prepared as in Experiment 155. 
Small pieces of cotton fabric dyed or printed in various 
colors. 
Immerse the pieces of cotton in the bleaching-powder solution 
for a few minutes. Then dip in dilute hydrochloric acid. Repeat 
the treatment with bleaching powder and dilute hydrochloric 
acid several times, noting the effect on the colors. 

Experiment 157. — Effect on Textile Materials. 

Materials : 

Bleaching-powder solution prepared as in Experiment 

Sodium bisulphite solution or sodium thiosulphate solu- 
tion. 
White or unbleached cotton, linen, silk, and Wool, in yarns or 
light fabrics. 
Immerse the textiles in the bleaching-powder solution for a 
few minutes, then dip in dilute hydrochloric acid, and finally in 
sodium bisulphite solution. Rinse and dry. Note how the color 
and strength of the materials have been affected. 



246 ELEMENTARY HOUSEHOLD CHEMISTRY 

Experiment 158. — Formation of Oxycellulose. 

Materials : 

White cotton or linen goods. 
Bleaching-powder solution. 
Sodium bisulphite solution. 
Immerse three equal-sized pieces of the goods in the bleaching- 
powder solution for about five minutes. Dry one without rinsing. 
Treat the second with dilute hydrochloric acid and the third with 
sodium bisulphite (or with sodium thiosulphate) solution ; rinse 
and dry. 

When the three pieces are dry, compare their strengths and 
colors. 

Experiment 159. — Detection of Oxycellulose. 

Thoroughly wash the piece of cotton dried with the bleaching 
powder in it (Expt. 158). Cover it with Fehling-Benedict solution 
and boil. For comparison boil a piece of untreated cotton with 
Fehling-Benedict solution. Oxycellulose reduces the solution, 
the precipitate of cuprous hydroxide being deposited upon the 
fiber. 

Industrially, silk is never treated with bleaching powder 
or other hypochlorites. In the woolen industry bleaching 
powder is not used for bleaching purposes, though it is 
sometimes used to render woolen goods unshrinkable — not, 
however, without injury to the wearing qualities. In the 
commercial bleaching of cotton and linen, however, it is 
universally used. Great care has to be exercised to prevent 
the formation of oxycellulose, which both tenders the goods 
and makes them dye unevenly. Special care is necessary in 
the case of linen, which has more natural color to remove 
and at the same time has a more easily injured fiber than 
cotton. Weaker solutions are used for linen, the treatments 
being more numerous and the bleaching-powder treatment 
(" chemicking ") being alternated with treatments with 
alkalies and supplemented by grass bleaching. 

Cotton bleaching is accomplished by alternate treatments 
with bleaching-powder solution (" chemicking ") and with 



BLEACHING AND BLUEING 247 

dilute hydrochloric acid (" souring "). The acid acts on the 
bleaching powder left in the material, converting it into 
chlorine and calcium chloride, which are readily washed out. 
If solid particles of bleaching powder are allowed to come 
into contact with the goods, or if the goods are exposed to 
air and light before the hypochlorite has been completely 
removed, oxy cellulose is apt to be formed. Much damage 
is no doubt done in domestic and commercial laundries 
through the ignorant use of bleaching powder. Washing 
with water ought not to be depended upon to remove the 
reagent from the goods. Effective materials for this purpose, 
less disagreeable in their effects than the hydrochloric acid 
(which is preferred in factory practice for economical reasons), 
are sodium bisulphite, NaHSOs, and sodium thio sulphate, 
Na2S203, commonly known as hyposulphite of soda. 

Experiment 160. 

Materials : 

Bleaching-powder solution. 
Pieces of dyed or printed cotton. 
To a filtered solution of bleaching powder add sodium carbonate 
solution as long as a precipitate is formed. The precipitate is 
calcium carbonate. Write equation for the reaction. What com- 
pounds are left in solution? Filter. 

Immerse pieces of colored cotton in the liquid, afterwards treat- 
ing with dilute hydrochloric acid. 

The solution obtained by the interaction of sodium car- 
bonate and chloride of lime contains sodium chloride and 
sodium hypochlorite. The latter has a bleaching action 
similar to that of the calcium compound and has the ad- 
vantage of avoiding the impregnation of the goods with cal- 
cium salts which may afterwards react with soaps, producing 
deposits of the insoluble lime soaps. It finds use in the house- 
hold for the removal of stains from fabrics by bleaching. 

Sodium hypochlorite can also be prepared by passing chlorine 
gas into a dilute, cold solution of sodium hydroxide or sodium 



248 ELEMENTARY HOUSEHOLD CHEMISTRY 

carbonate and by passing an electric current through a solution 
of common salt. In either case the solution obtained contains 
sodium chloride as well as sodium hypochlorite. 

This solution is popularly known as Javel water (commonly 
misspelled Javelle or Javelles) although that name belonged 
originally to the corresponding potassium product, which was first 
made in the Javel bleach works near Paris in 1792. In pharmacy 
the sodium solution is known as Labarraque's solution. 

Hydrogen Peroxide 

Hydrogen peroxide is a compound of hydrogen and oxygen 
containing a higher percentage of oxygen than does water. 
Its formula, H2O2, expresses the fact that the proportion of 
oxygen to hydrogen is twice as great as in water, H2O; in 
other words, that its molecule contains two atoms of oxygen 
combined with two atoms of hydrogen. In acting as an 
oxidizing agent hydrogen peroxide gives up half its oxygen 
(i.e. one atom from each molecule), and water remains. 

Pure hydrogen peroxide is a liquid resembling water, but 
heavier and more viscous. It is an unstable substance, de- 
composing spontaneously into water and oxygen. For this 
reason it is not easy to make or to keep, and the common 
commercial hydrogen peroxide is only a 3 per cent aqueous 
solution. 

As a bleaching agent hydrogen peroxide has the advantages 
over all others, except oxygen and ozone, that it does not 
injure the most sensitive of the textile fibers and that it 
leaves no solid residue in the goods. It is used in a mildly 
alkaline medium, being less stable in alkaline than in acid 
solutions and therefore more rapid in its action. It is em- 
ployed in the bleaching of feathers and ivory. 

Experiment 161. 

Materials : 

Hydrogen peroxide solution. 
Manganese dioxide, powdered. 
Feather. 



BLEACHING AND BLUEING 249 

Colored hair. 
Ecru silk. 
To 5 cc. hydrogen peroxide in a test tube add a little powdered 
manganese dioxide. Test the evolved gas with a glowing splint. 
What is the gas? 

To 10 cc. hydrogen peroxide in a beaker add ammonium hy- 
droxide little by little until small bubbles begin to form. Immerse 
the feather, hair, and ecru silk, and examine from time to time. 

The great disadvantage of hydrogen peroxide as a bleach- 
ing agent is its high price. This can to some extent be 
obviated by preparing the hydrogen peroxide in the bleach- 
ing bath itself from cheaper materials. Sodium peroxide, 
Na 2 2 , is one of the materials from which it is obtained. 
Sodium peroxide reacts with acids, liberating hydrogen per- 
oxide, thus : 

Na 2 2 + H 2 S0 4 = Na 2 S0 4 + H 2 2 

In use the sodium peroxide is gradually added to cold 
water. The solution thus obtained is neutralized with dilute 
sulphuric acid and then rendered mildly alkaline by the 
addition of sodium silicate. 

Sodium perborate, NaBOs . 4 H 2 0, is also used as a bleaching 
agent, its solution behaving like one of borax and hydrogen 
peroxide. 

Potassium permanganate, KMn0 4 , is occasionally used as a 
bleaching agent. In acting as an oxidizing agent it yields a brown 
solid residue. This residue is removed by treatment with sodium 
bisulphite. 

The nature of sunlight bleaching is obscure. It is possible that 
the action of the sunlight on the evaporating water produces 
hydrogen peroxide or ozone (an active form of oxygen), and that 
this product acts upon the coloring matters. 

Sulphurous Acid 
Experiment 162. 

Materials : 
Sulphur. 

Red flower or fresh grass. 
Pieces of colored cotton. 



250 ELEMENTARY HOUSEHOLD CHEMISTRY 

Apparatus : 

Deflagrating spoon. 
Glass cylinder or beaker. 
Glass plate. 
Ignite a small quantity Q gram) sulphur in a deflagrating spoon, 
lower the spoon into the beaker and cover with the glass plate. 
Note odor of gas evolved. This gas is sulphur dioxide, S0 2 . Sus- 
pend in the beaker a red flower {e.g. rose or carnation) or some 
grass and some pieces of colored cotton. 

Experiment 163. 

Materials : 

Sodium bisulphite. 
Potassium permanganate solution. 
Apparatus : 
Test tube with one-holed rubber stopper or cork, through 
which passes a delivery tube bent twice at right angles so 
as to reach the bottom of a second test tube. 
Place in the generator test tube 1-2 grams sodium bisulphite, 
cover with water, and add a few cubic centimeters of dilute sul- 
phuric acid. Fill the other test tube with water and pass the gas 
from the generator into the water. Note the odor of the gas and 
compare it with that obtained by burning sulphur (Expt. 162). 
What is the gas? Write equation for its formation. Does it 
appear to be absorbed by the water? (Compare size of bubbles 
as they leave the tube with those which escape from the water.) 
Test the water with blue litmus paper. What do you infer as to 
the character of the substance formed by the combining of the 
gas with water? Write equation for this reaction. The solution 
contains sulphurous acid. Try the action of this solution on the 
same materials as were exposed to the action of the gas in Experi- 
ment 162. Add a little of the solution to a dilute solution of 
potassium permanganate. 

Experiment 164. 

Materials : 

Sodium bisulphite. 

Indigo carmine solution, prepared by dissolving indigo carmine 
in water or by warming 1 gram indigo with 8 cc. fuming 
sulphuric acid for one to two hours, rinsing into a flask and 
making up to 1 liter. 



BLEACHING AND BLUEING 251 

To indigo carmine solution add sodium bisulphite solution 
sufficient to discharge the blue color. To one portion of the prod- 
uct add dilute sulphuric acid, to a second ammonium hydroxide. 

Sulphurous acid, H2SO3, is known only in solution. Its 
anhydride is the gas sulphur dioxide, SO2. Being dibasic, 
sulphurous acid forms acid salts, e.g. sodium bisulphite, 
NaHSOs, as well as the normal salts, such as sodium sulphite, 
Na2S03. The anhydride, the acid, and the acid sodium salt 
are all used as bleaching agents in the textile industries. 
The gaseous anhydride, sulphur dioxide, finds the widest 
use. The usual method of bleaching wool and silk is to burn 
sulphur in iron or brick pans in a chamber in which the 
goods are suspended. The process is known technically as 
" stoving." As a little sulphuric acid is formed in the burn- 
ing of sulphur, thorough washing should follow stoving. 

For bleaching on a small scale sodium bisulphite is con- 
venient. The goods may either be steeped for some hours 
in a fairly strong (about 15 per cent) solution of the bisulphite, 
then passed through very dilute hydrochloric acid, and finally 
washed with water ; or a weak solution of the bisulphite 
may be acidified with hydrochloric acid and the goods 
soaked several hours in the mixture, which, of course, con- 
tains free sulphurous acid. 

Wool bleached with sulphurous acid or bisulphite is readily 
affected by alkalies, the natural yellow color returning on 
washing with soap or soda. 

A more permanent bleach is obtained by the use of hydro- 
gen peroxide. Black or brown wools and hair cannot be 
bleached white, but assume a golden color when treated with 
peroxide. 

Blueing 

In addition to bleaching, i.e. chemical alteration of the 
coloring matters, there is another device used, both indus- 
trially and in the household, to give yellowish goods a pure 



252 ELEMENTARY HOUSEHOLD CHEMISTRY 

white appearance. Blue and yellow, being complementary 
colors, neutralize each other in their optical effect. Yellow- 
ish goods can therefore be made white by treatment with a 
suitable quantity of blue coloring matter. The materials 
used for this purpose are : 

i. Ultramarine, a complex compound of the elements 
sodium, aluminium, silicon, sulphur, and oxygen. Originally 
found as a rather rare mineral, lapis lazuli, ultramarine is 
now made synthetically from sodium sulphate, clay, and 
sulphur by heating with a carbonaceous reducing agent, 
such as charcoal or tar. Ultramarine is insoluble in water, 
but in a finely divided condition remains suspended long 
enough to be evenly distributed over the goods. It is not 
affected by air, light, or alkalies, but is decomposed by dilute 
acids. 

2. Indigo, a dye formerly, and to some extent still, ob- 
tained by the fermentation of the juices of certain species of 
plants known as Indigoferce, but now manufactured in a 
purer form from coal-tar products. Indigo is insoluble in 
water, but can be suspended in it in the same way as ultra- 
marine. By treatment with fuming sulphuric acid it can 
be converted into indigo carmine (sulphindigotic acid), a 
soluble product retaining the blue color. It is not decolor- 
ized by acids, soap, or soda, and is fast to light. Suspended 
indigo can be decolorized by treatment with sodium bisul- 
phite and zinc dust, indigo carmine by sodium bisulphite 
alone. 

3. Soluble Coal-tar Products. — Blues of this class can 
often be recognized by making one portion of the solution 
acid and another alkaline and comparing colors. The two 
will usually differ in shade. The best coal-tar blues are not 
actual dyes, which would permanently color the textile, but 
rather substances which will readily wash out, e.g. the 
alkali blues and indigo carmine. 

All the above are good stable blues. The soluble blues — ■ 



BLEACHING AND BLUEING 253 

including indigo carmine — have the advantage over the in- 
soluble that they give a more even coloring to the fabric. 
Some of them, however, are treated with oxalic acid in the 
laundry to set them in the goods, and the acid, drying in 
the fabric, corrodes the textile fibers. 

A cheap but very objectionable laundry blue is Prussian, 
or Berlin, blue. This is a compound of iron, carbon, and 
nitrogen, the chemical name for which is ferric ferrocyanide. 
It is decomposed by alkalies with production of ferric hy- 
droxide, Fe(OH)3. Goods treated with it are apt to show 
rust stains, particularly if they contain any soap or soda 
when blued. 

Experiment 165. 

Materials : 

Ultramarine. 

Prussian blue. 

Indigo. 

Soluble blues. 

Soap solution. 
Place a minute quantity of each blue in a separate test tube. 
Fill with water and shake until the blue is evenly distributed 
through the water. 
Test portions of each liquid with the following solutions : 

(a) Dilute hydrochloric acid. Note the odor from the ultramarine. 
Moisten a piece of filter paper with lead acetate solution and hold 
,at the mouth of the test tube. 

(b) Sodium hydroxide. Compare the colors with those of the 
acidified solutions from (a). 

(c) Sodium carbonate. 

(d) Soap, boiling. 

Allow the main portions to stand for a few days and note which 
form sediments. 



CHAPTER XLIII 

DYEING 

Dyeing consists in attaching a colored substance to the 
fibers of the textile in such a manner that it is not readily 
removed by rubbing or washing. Whether dyeing involves 
a chemical union between the fiber and the coloring matter 
is a disputed question. There are some facts which appear 
to indicate that such combinations of fiber and dye do occur 
in some instances. The animal fibers (and leather), being 
protein and having, therefore, basic and acid radicles, will 
combine directly with certain dyes which are acid and basic, 
whereas the same dyes will not become attached to the vege- 
table fibers. On the other hand, the product of the deposi- 
tion of the dye in the fiber does not appear to have properties 
distinct from those of the dye and of the fiber, which ought 
to be the case if actual combination has occurred ; nor does 
the combination seem to occur in the definite proportions in 
which substances react in chemical processes, but this may 
be because the enormous size of the protein molecules makes 
possible an almost unlimited number of compounds. The 
fact that cotton fibers from which the lumen is absent refuse 
to take dyes furnishes another argument in favor of a physical 
theory of dyeing. 

The protein fibers are so different in character from the 
cellulose fibers, and the diversity of chemical nature among 
dyestuffs is so great, that it is not likely that all cases of dye- 
ing can be explained in the same way. Physical phenomena 
may play the more important part in some instances, chemi- 
cal phenomena in others. 

Many dyes that will not attach themselves directly to a 

254 



DYEING 255 

given kind of fiber will dye the fiber after it has been first 
treated with a substance called a mordant (from the Latin, 
mordeo, I bite). The mordant is used to attach to the 
fiber a compound capable of combining with the dye to form 
an insoluble product. The insoluble product is known as a 
lake. 

A dye that will dye fibers without the intervention of a 
mordant is called a substantive dye. 

A dye that will only attach itself to the fiber through the 
intervention of a mordant is called an adjective or mordant 
dye. 

Practically all the modern dyes are organic compounds. 
A buff color of iron oxide is sometimes produced by treating 
the fabric first with an iron solution (such as ferrous sulphate), 
then with an alkali (e.g. sodium hydroxide or sodium car- 
bonate), and then exposing it to the air to oxidize the ferrous 
hydroxide, Fe(OH) 2 , formed at first, to ferric hydroxide, 
Fe(OH) 3 . " Khaki " is obtained by adding a chromium salt 
(chrome alum) to the iron solution and treating in this way, 
thus producing a mixture of ferric and chromic oxides. Man- 
ganese brown, composed of an oxide (or hydroxide) of man- 
ganese, can be similarly produced from solutions of manganese 
salts. Chrome yellow is produced as a precipitate in the 
fibers when the goods are treated first with lead acetate and 
then with potassium dichromate. These inorganic dyes are 
sometimes called " mineral pigments." 

Of the organic dyes a few are still obtained from plant or 
animal sources. Logwood, a dye extracted from the heart 
wood of a large South and Central American tree, the Haema- 
toxylon campechianum (literally, blood-red wood of Campeachy), 
is used extensively in the silk industry and in calico printing 
for the production of a full black. Quercitrin bark and Per- 
sian berry are still used in dyeing yellow, although better 
effects are, as a rule, obtained with synthetic dyes. 

Natural indigo, obtained by exposing to the air the juice 



256 ELEMENTARY HOUSEHOLD CHEMISTRY 

of the leaves of various species of plants of the genus Indigo- 
fera, formerly cultivated on a large scale in India, has within 
the last decade been almost entirely replaced -Jby synthetic 
indigo, the same compound in purer form manufactured 
from coal-tar products. 

Madder, obtained from the dried roots of the madder plant 
and used for the production of Turkey red, has long been 
replaced by synthetic alizarin, a compound identical with 
one of those contained in the natural product. Alizarin is 
manufactured from coal-tar products, and derivatives of the 
compound are in use which enable the dyer to obtain blues, 
purples, yellows, etc., chemically similar to Turkey red and 
equally fast to light and washing. Such vegetable dyes as 
sandalwood, archil, alkanet, fustic, turmeric, and cudbear, 
and such insect dyes as cochineal, kermes, and lac dye, have 
been replaced almost completely by coal-tar derivatives, not 
identical with the natural coloring matter of these sub- 
stances, but superior to them in fastness, in convenience, in 
economy, or in beauty. Cochineal, however, is still used to 
some extent. 

The synthetic {i.e. built-up) dyes are all derived from 
products of coal tar. The first to be manufactured were 
made from aniline, C 6 H 5 NH 2 , and the term " aniline dyes " 
is sometimes applied in popular language to the whole group 
of substances. Only a few of them, however, are actually 
made from aniline. Coal-tar dyes and synthetic dyes are more 
appropriate names for the class. Coal tar is obtained as a 
by-product when coal is heated out of contact with air, 
which is done in the manufacture of coke for fuel and coal 
gas for illuminating purposes. (See Chapter XII.) The 
tar is a mixture of an enormous number of organic com- 
pounds. Prominent among them are the hydrocarbons 
benzene, C 6 H 6 , naphthalene, CioHs* and anthracene, C14H10; 
the phenols, carbolic acid (phenol proper), CeHsOH, and 
the three cresols, C7H7OH ; and the amine, aniline, C 6 H 5 NH2. 



DYEING 257 

From these coal-tar products are derived, directly or in- 
directly, thousands of chemical compounds, among which 
are many coloring matters. Of these a considerable num- 
ber make good dyes. 

The coal-tar dyes may be classified as follows : 

1. Direct or Substantive Cotton Dyes. 

2. Developed Dyes. 

3. Mordant or Adjective Dyes. 

4. Acid Dyes. 

5. Basic Dyes. 

1. Direct or Substantive Cotton Dyes 

These dye cotton without the intervention of a mordant. 
Their application is so simple and inexpensive that they are 
very commonly used, although as a class they are excelled 
in fastness by the mordant dyes and in brilliance by the 
basic colors. The transfer of dyes of this class from solution 
to the fibers is accelerated by the addition of salts, especially 
sodium chloride and sodium sulphate, to the solution. 
Hence the name " salt colors " sometimes applied to this 
class of dyes. Alkalies, on the other hand, tend to retard the 
precipitation of the coloring matter into the fiber. Sodium 
carbonate, sodium phosphate, and soap are sometimes added 
to the bath to render the dyeing slower and more penetrative. 

In washing goods dyed with dyes of this class the soda 
and soap used tend to cause " bleeding " of the dye, while 
salt added to the water will sometimes prevent this trouble. 
In many instances the fastness of a substantive dye to wash- 
ing is improved by after treatment with metallic salts or with 
formaldehyde. 

In other instances the material originally deposited is con- 
verted into another and faster dye by a developing process. 
Many of the dyestuffs contain amino ( — NH2) groups, and 
it is these which are used for this purpose. After the sub- 



258 ELEMENTARY HOUSEHOLD CHEMISTRY 

stantive dye containing an amino group is applied, the 
goods are treated with nitrous acid (HNO2). This reagent 
converts the amines in the fiber into unstable, compounds 
known as diazonium salts. The conversion of an amine into 
a diazonium salt is called diazotizing. When a diazonium 
salt is brought into a solution containing another amine or a 
phenol, a reaction takes place by which the molecule of the 
amine or phenol is combined with that of the substantive dye 
through two nitrogen atoms, the product being a dye faster 
than that originally applied and sometimes also of a different 
color. The yellow dye, primuline, for instance, can be de- 
veloped into a red dye by diazotizing and coupling with 
/?-naphthol. 

Experiment 166. — Dyeing Cotton with a Substantive Dye. 

Materials : 

Skein of cotton yarn. 
Primuline. 
Salt. 
Dissolve 0.3 gram of primuline and 1 gram of salt in just 
sufficient water to cover 5 grams of the cotton. Add about ^ cc. 
sodium carbonate solution. Heat to 6o° C. (140 F.), introduce 
the 5 grams of cotton, and gradually heat to boiling. BoiL 15 to 
30 minutes. Note the color. Rinse in cold water. 

Experiment 167. — Development of a Substantive Dye by Diaz- 
otizing. 

Materials : 

Dyed skein of cotton from preceding experiment. 
Sodium nitrite. 
/?-naphthbl. 
Dissolve 0.25 gram sodium nitrite in sufficient water to cover 
the goods. Add 3 cc. dilute sulphuric acid. What acid is pro- 
duced ? Immerse the dyed skein of cotton for 10 minutes, keeping 
the bath cool. Does the color change? 

Rinse in acidulated water and immediately transfer to a bath 
containing 0.1 gram /3-naphthol dissolved in an equal weight of 
a 30 per cent solution of NaOH. Note the production of the new 
color. 



DYEING 259 

Although called direct cotton dyes, many of this class give 
even better results on wool. This is especially true of the 
reds and yellows. 

Closely related to the substantive dyes, at least in the 
manner of their application, are the so-called " sulphur 
dyes." These are applied in a salt bath to which sodium 
sulphide has been added. They are used exclusively on 
cotton and linen. They are exceedingly fast to washing. 

2. Developed Dyes 

The developed dyes are those whose colors are produced 
within the fiber. They may be produced (a) by oxidation 
of a soluble compound to an insoluble dye or (b) by combin- 
ing two colorless or slightly colored compounds into a dye by 
diazotizing. 

The " vat " dyes and aniline black are examples of the 
first class. The vat dyes, of which indigo is the oldest ex- 
ample, are reduced to so-called " leuco compounds " by strong 
reducing agents. The leuco compounds, being soluble, pene- 
trate the fiber. The goods are then exposed to air for 
15 to 20 minutes, after which they are boiled in a soap solu- 
tion. This treatment reoxidizes the leuco compound to the 
insoluble dye. The vat colors are characterized by extreme 
fastness, not only to light and washing, but also to the action 
of acids, alkalies, and oxidizing agents. 

The reduction of indigo was formerly accomplished by a 
fermentation, whence the term " vat." The reducing agent 
now almost universally used for all vat colors is sodium hydrc- 
sulphite, Na2S204, which is prepared by reducing sodium 
bisulphite with zinc dust. Sodium hydrosulphite is very 
readily oxidized by the oxygen of the air. A compound of 
sodium hydrosulphite with formaldehyde, which is less 
affected by the air, is sometimes used instead of the sodium 
hydrosulphite itself. 



260 ELEMENTARY HOUSEHOLD CHEMISTRY 

Experiment 168. — Vat Dyeing with Indigo. 

Materials : 

Sodium bisulphite solution (30 per cent) and zinc dust. 
Indigo powder or paste. 
Sodium hydroxide (30 per cent). 
Cotton skein or piece of cheesecloth. 

To 1 gram zinc dust in a test tube add 10 cc. of the sodium 
bisulphite solution. Allow to stand for a few minutes, stirring 
gently from time to time with a glass rod. The sediment should 
become pale gray. What compound is produced by this action ? 

In another test tube place 1 gram powdered indigo or 2.5 grams 
indigo paste, 20 per cent. Add 8 cc. of the concentrated sodium 
hydroxide solution and mix. Add the contents of the other tube, 
heat to 50 C. (120 F.), and set in a beaker of water at 50 C. 
Allow to stand until the material has turned yellow (about \ hour) . 
Sufficient material is obtained for 3 or 4 students to perform the 
actual dyeing, which is done as follows : 

Into 50 cc. water put a very little zinc dust (0.1 gram) and sodium 
bisulphite solution (0.5 cc). This removes the dissolved oxygen 
from the water. Add about one fourth of the yellow liquid. Wet 
the cotton, immerse it for a minute or so, squeeze it out well, and 
hang it exposed to the air for 5 or 10 minutes. Note the develop- 
ment of the color. Rinse with water, soap to remove unabsorbed 
dye, and rinse again. 

Sodium hydrosulphite, or its formaldehyde compound, may be 
used instead of the zinc and sodium bisulphite. Use 2 grams 
sodium hydrosulphite and 20 cc. water for 2 grams indigo, and 
allow to stand 10 minutes before adding the sodium hydroxide, 
of which only half as much will be required as when the bisulphite 
is used. Heat to 6o° C. (140 F.) and allow to stand until a glass 
rod dipped into the mixture gives a clear yellow drop and the 
liquid wetting the rod becomes blue after about half a minute's 
exposure to the air. A little hydrosulphite should be used to 
remove the dissolved oxygen from the diluting water. 

Aniline black is a color so fast to washing that it forms 
the basis of many marking inks. It is an oxidation product 
of aniline, C 6 H 5 NH 2 , produced not by the action of atmos- 
pheric oxygen, but by that of oxidizing agents. Pure aniline 
is a colorless, oily liquid, insoluble (or rather only slightly 
soluble) in water, and possessed of a penetrating, somewhat 



DYEING 261 

nauseating odor. The ordinary " aniline oil " of commerce 
is, however, colored yellowish brown by impurities. Being 
an amine, aniline forms salts with acids, similar to the 
ammonium salts, e.g. aniline hydrochloride, C 6 H 5 NH 3 C1. 
These salts are soluble in water. In dyeing with aniline 
black the goods are impregnated with an oxidizing agent 
such as potassium (or sodium) chlorate, with an aniline salt, 
and with a catalytic agent, such as copper sulphate or sodium 
ferrocyanide. They are then exposed to the action of steam 
for half a minute and afterwards treated with soap. The 
heat and moisture promote the oxidation. Aniline black 
can also be obtained directly from aniline by oxidizing it 
with a mixture of potassium dichromate and sulphuric acid, 
as in the following experiment. 

Experiment 169. — Dyeing with Aniline Black. 

Materials : 
Aniline oil. 

Potassium dichromate solution (5 per cent). 
Cotton skein or cheesecloth. 
Note odor and appearance of commercial aniline. Shake about 
1 cc. with water (5 cc). Add concentrated hydrochloric acid and 
shake again. 

To 100 cc. potassium dichromate solution add 250 cc. water 
and 10 cc. dilute (2 N.) sulphuric acid. Dissolve if cc. aniline 
in 2\ cc. concentrated hydrochloric acid and add to the dichromate 
mixture. Immerse the cotton and slowly heat the bath to 8o° C. 
(17 5 F.). Rinse well, soap, wring out, and dry without rinsing 
out the soap. 

On account of the use of the strong " mineral " acids, 
aniline black dyeing is apt to injure the fiber. The use of 
sodium (or potassium) ferrocyanide, Na 4 Fe(CN) 6 , as a catalytic 
agent appears to mitigate this evil. It reacts with the mineral 
acid, e.g. hydrochloric, giving sodium chloride and ferro- 
cyanic acid, H 4 Fe(CN) 6 , a weaker acid than hydrochloric. 

The second class of developed synthetic dyes embraces 



262 ELEMENTARY HOUSEHOLD CHEMISTRY 

those which are produced by saturating the goods with the 
solution of a colorless compound (technically a " prepare "), 
then introducing them into a diazotized solution of an amine 
— in other words, into the solution of a diazonium salt. The 
principle is exactly the same as that of the after- development 
of substantive colors, described above (p. 257), and the 
product is an insoluble dye, precipitated within the fiber. 
The diazonium salts are only stable at low temperatures. 
Ice is therefore kept in the developing solution. On account 
of this circumstance colors produced by this process are 
called " ice colors." 

The " prepare " universally used for ice colors is a solution 
of sodium /3-naphtholate, prepared by dissolving /3-naphthol 
in caustic soda. Several beautiful reds are produced by this 
process, and blue and black can also be obtained. 

Experiment 170. — Dyeing with Paranitraniline Red. 

Materials : 

Skein of white cotton yarn or piece of cheesecloth. 

Paranitraniline. 

(3-naphthol. 

Sodium nitrite. 

Sodium acetate crystals. 

Sodium hydroxide solution (30 per cent). 
Dissolve 3 grams /3-naphthol in 100 cc. water to which have been 
added 3 cc. of the strong sodium hydroxide solution. 

In a 250 cc. beaker, heat 7 grams paranitraniline with 4 cc. cone, 
hydrochloric acid and 75 cc. water. Paranitraniline hydrochloride 
is formed. When all has dissolved, cool quickly, stirring rapidly 
so as to make the hydrochloride crystallize out in small crystals. 
Continue the cooling below the room temperature by putting ice 
into the beaker. When the temperature reaches 4 C. (39 to 
40 F.), gradually add 4 cc. concentrated hydrochloric acid, then 
throw in 3.5 grams sodium nitrite. Keep down to 4 C. by adding 
more ice as needed. After 10 or 15 minutes add 8 grams sodium 
acetate crystals. 

Immerse the cotton in the /3-naphthol " prepare," wring out 
gently, dry carefully, and immerse in the cold diazonium salt 
solution. Work the cotton in the solution for a minute or so. 



DYEING 263 

Remove, rinse well, dip into water to which a little sodium car- 
bonate has been added, then rinse again thoroughly. 

Instead of the paranitraniline the following may be used in the 
experiment, the red colors obtained varying in shade from para- 
nitraniline red: a-naphthylamine (7 grams), /3-naphthylamine 
(7 grams), benzidine (4.5 grams), metanitraniline (7 grams). 

3. Mordant or Adjective Dyes 

The mordant or adjective dyes may be either of acid or of 
basic character. In the case of the acid dyestuffs the mor- 
dants used are of such a character that they leave upon the 
fiber, and firmly combined with it, metallic bases which are 
capable of combining with the acid dyestuff. Soluble salts 
or soluble basic salts of the weak bases are suitable. Those 
used practically are salts of aluminium, iron, chromium, tin, 
copper, cobalt, and nickel. The goods are immersed in solu- 
tions of the salts and then either subjected to the action of a 
weak alkali, or, in case the acid of the salt is a volatile one, 
are steamed to liberate the weak acid and drive it off as vapor. 

As a rule, goods prior to drying are subjected to the process 
of " dunging," which in the practice of half a century ago 
consisted in passing the goods through cow dung. Later, 
arsenate of soda was substituted, but phosphate of soda has 
now superseded this poisonous compound. The effect of 
the dunging process is to fix the mordant more firmly in the 
fiber and thus enhance the fastness of the dye subsequently 
to be applied. The dunging process has also the effect of 
removing the surplus mordant so as to insure an even surface 
of the goods ("level dyeing"). Afterwards the goods are 
dyed, the dyestuff combining with the metallic base to form 
a lake, often different in color from the dyestuff itself. 

Experiment 151. — Alizarin Lakes. 

Materials : 

Alizarin. 

Solutions of aluminium, chromium, and ferrous salts. 
Dissolve a little alizarin in ammonia. To separate portions 



264 ELEMENTARY HOUSEHOLD CHEMISTRY 

of the solution, add calcium sulphate and small quantities of the 
aluminium, chromium, and ferrous solutions. Heat to boiling 
and filter. Note the colors of the precipitates. Wash them on 
the filter. Do they retain the dye? 

For comparison precipitate the hydroxides of the metals by 
adding ammonium hydroxide to the solutions. 

As an auxiliary to the mordant base, an acid mordant or 
fixing agent is sometimes employed. The leading examples 
of this class of bodies are : (1) the tannins , (2) fatty acid deriva- 
tives. The tannins or tannic acids are much used with the 
basic dyes (see below) and as weighting agents for silk. (See 
Chapter XL.) Cotton which is to be mordanted with iron, 
tin, or aluminium salts is sometimes first treated with a tan- 
nin, usually sumac extract. 

The most important fatty acid derivative used as a fixing 
agent is Turkey-red oil. This is prepared by treating castor 
oil or olive oil with concentrated sulphuric acid, keeping the 
mixture cold. The product is soluble in water, but it is cus- 
tomary to partially neutralize with caustic soda or ammonia 
to render it more soluble. It takes its name from its use in 
Turkey-red dyeing. The dye used in this process is alizarin, 
and before the discovery of Turkey-red oil the mordanting 
of the cotton, preliminary to dyeing with extract of madder 
root, was a very lengthy process, requiring several weeks 
for its completion. Nowadays the goods are treated with 
Turkey-red oil, dried overnight, mordanted in an aluminium 
solution, dried again overnight, treated with a mild alkali 
(usually chalk), dyed with synthetic alizarin, steamed, 
soaped, rinsed, and dried. The whole process is completed 
in three days, and the result compares favorably with that 
obtained by the old process. Slightly rancid olive oil and 
soaps containing a little free fatty acid are other materials 
used with alizarin and dyes chemically related to it. Some- 
times tannins and fatty acid fixing agents are both used with 
these dyes. 



DYEING 265 

4. Acid Dyes 

The acid dyes dye wool and silk directly. They are very 
seldom used on cotton. They are usually sold in the form 
of their sodium salts, and are liberated in the dyeing bath by 
treatment with an acid, usually sulphuric. Sodium sulphate 
is used as a restraining agent, preventing too rapid absorp- 
tion of the dye. This is just the opposite effect from that 
played by sodium sulphate in dyeing cotton with direct dyes. 

There is great variety among the acid dyes, and they play 
a very important part in the dyeing of wool and silk. The 
best of them are very fast to light, although not equal to the 
vat dyes in this respect. They are not fast to washing with 
soap. 

5. Basic Dyes 

The basic dyes, which are the real aniline derivatives, are 
applied to wool and leather directly (rarely to silk) and to 
cotton mordanted with tannin. Chardonnet artificial silk 
(p. 239) takes these dyes better than those of any other class. 
They are characterized by great brilliance, but very few of 
them are fast to light. In cotton dyeing they are often used 
to " top " other dyes. The brightness of sulphur dyes can 
be increased by such topping, and so also can the fastness of 
the substantive dyes to washing. 

The chief tannins used as mordants or fixing agents for 
the basic dyes are those derived from : (1) gallnuts, which 
are excrescences produced on oak trees and other plants as 
the result of insect injuries ; (2) sumac leaves and twigs ; 
(3) catechu; (4) horse-chestnut wood. Cotton immersed in 
tannin solutions absorbs more or less of the tannins. The 
tannin behaves as an acid, weak but polybasic, i.e. having 
several replaceable hydrogen atoms. The cotton is next 
treated with an antimony salt, usually potassium antimonyl 
tartrate, tartar emetic. An insoluble antimony tannate, or 
acid antimony tannate, is produced in the fiber, and this has 



266 ELEMENTARY HOUSEHOLD CHEMISTRY 

sufficient replaceable hydrogen left to act as an acid towards 
the basic dye. In dyeing, a double tannate of antimony and 
the dyestuff is formed in the fiber. 



\ 



Calico Printing 

Designs on cotton are produced by means of printing 
machines, which consist essentially of rollers upon which 
the design, or so much of it as is to be printed in one color, 
is engraved. The rollers may be employed either (i) to 
apply the dyestuff, thickened with starch or gum, directly 
to the goods, (2) to print upon the goods a mordant which 
will fix a dye to be subsequently applied, (3) to print upon 
the goods a reagent which will resist the action of a dye to 
be subsequently applied, (4) to print upon dyed goods a re- 
agent which will discharge the dye by converting it into a 
colorless compound, or by removing the mordant which 
holds the dye, or (5) to print both a discharging agent and a 
new dye or mordant. 

Practically all the dyes which are applicable to cotton can 
be used in printing processes. 



APPENDIX A 

LIST OF TABLES IN APPENDIX A 

Table Subject 

I. Foods of Vegetable Origin — Average Composition and 

Nutritive Value. 
II. Foods of Vegetable Origin — Important Ash Constitu- 
ents in the One-Hundred-Calorie Portion of Edible 
Material. 

III. Foods of Animal Origin — Meats — Average Composition 

and Nutritive Values. 

IV. Foods of Animal Origin — Composition of Meats, Fat 

and Lean. 
V. Foods of Animal Origin — Fish — Average Composition 

and Nutritive Value. 
VI. Foods of Animal Origin — Dairy Products — Average 

Composition and Nutritive Value. 
VII. Miscellaneous Foods of Animal Origin — Average Com- 
positions and Nutritive Value. 
VIII. Foods of Animal Origin — Important Ash Constituents 
in the One-Hundred-Calorie Portion of Edible 
Material. 
IX. Approximate Weights of One Cupful of Some Food 
Materials. 

TABLES 

The following tables of food composition are derived, for the 
most part, from the compilations of Atwater and Bryant, 1 of 
Sherman, 2 and of Rose. 3 

1 Atwater and Bryant, " Chemical Composition of American Food Materi- 
als," Office of Experiment Stations, United States Department of Agriculture, 
Bulletin 28, Revised edition, i8gg. These tables are also to be found in the 
appendix to Jordan's " Principles of Human Nutrition," New York, 191 2. 

2 Sherman, " Chemistry of Food and Nutrition," New York, 191 1. 

3 Rose, "A Laboratory Hand-Book for Dietetics," New York, 1913. 

267 



268 APPENDIX A 

Note. In the tables of Atwater and Bryant (Bulletin 28) and in the data 
drawn from them by Jordan, the fuel values are calculated by factors which 
are now known to have allowed too little for losses in digestion and which 
gave results from 2.5 to 3.3 per cent too high. The fuel values given here (as 
well as those in the tables of Sherman and of Rose) are recalculated by the later 
and more accurate factors as given in the foregoing text ; viz. protein and 
carbohydrate, 4 Calories per gram ; fat, 9 Calories per gram. These factors 
are equivalent to 1814 Calories per pound for protein and carbohydrates and 
4082 Calories per pound for fat. The fuel values in the tables are calculated 
to the nearest 5 Calories and, consequently, do not coincide exactly with those 
given by Sherman and by Rose. 

Table I gives the composition and nutritive value of selected foods 
of vegetable origin, arranged in groups, and Tables III-VII those of 
selected foods of animal origin. In these tables there is first given 
the per cent of refuse — peel and stems of fruit, bone and tendons 
of meat, etc., in short all the material that is not usable as food. 
The remaining columns all refer to the edible portion of the food. 
The percentage composition of the edible portion (omitting the 
ash) is next given, then fuel value in calories per pound. 

From these data the remaining figures of the tables are cal- 
culated as follows : 

1. The one hundred Calorie portion in ounces by dividing 1600 
by the fuel value per pound. 

Examples 

Bananas 1 

Fuel value per pound 450 Calories 

450 Calories are yielded by 16 ounces 

.'. 100 Calories are yielded by 1600 -5- 450 = 3.6 ounces 

Watermelons l 

Fuel value per pound 135 Calories 

100-Calorie portion in ounces 1600 -f- 135 = 11.9 

Dates 1 

Fuel value per pound 1575 Calories 
100-Calorie portion in ounces 1600 -5- 1575 = 1.02 

2. The distribution of the 100 Calories by multiplying the per 
cent of fat by 2.25, adding the per cent of protein and the per cent 
of carbohydrate, dividing the sum by each addend, and multiplying 
the result by 100. 

1 In all cases the data given relate to the edible portion of the food. 



APPENDIX A 269 

Examples 
Bananas 

Per cent of fat in the edible portion 0.6 

0.6 lb. fat is equivalent to 0.6 X 2.25 = 1.35 lb. protein or 

carbohydrate 
Per cent of protein 1.3 

Per cent of carbohydrates 22.0 

Sum 24.65 

Out of every 24.65 Calories the protein contributes 1.3 

_ . /-i 1 • 1 • -i i-3 X 100 

Out of every 100 Calories the protein contributes = 5, 

approximately 2 ^' * 

Out of every 24.65 Calories the fat contributes 1.35 

Out of every 100 Calories the fat contributes - - = 6, 

approximately 2 4' 5 

Out of every 24.65 Calories the carbohydrate contributes 22.0 

Out of every 100 Calories the carbohydrate contributes 

22.0 X 100 . 

= 89, approximately 

24.65 

Olives 

Fat 27.6 per cent, equivalent in 

fuel value to 27.6 X 2.25 = 60.1 per cent protein or 

carbohydrate 
Per cent of protein 1.1 

Per cent of carbohydrate 11.6 

Sum 72.8 

Out of 72.8 Calories the proteins yield 1.1 

Out of 100 Calories the proteins yield — =1.5 Calories 

72.8 

Out of 72.8 Calories the fats yield 60.1 

^ r r^ i • 1 r • i i ^O. I X IOO 

Out of 100 Calories the fats yield = 82.5 

72.8 

Out of 72.8 Calories the carbohydrates yield 11.6 

Out of 100 Calories the carbohydrates yield — '- = 16 

72.8 



270 APPENDIX A 

Pork, salt, clear fat 

Fat 86.2 per cent, equivalent to 86.2 X 2.25 = 194.0 proteins or 

carbohy- 
drates 

Protein 1.9 

Sum 195.9 
Out of 195.9 Calories proteins yield 19 

Out of 100 Calories proteins yield — — = 1 Calorie 

195-9 
Out of 195.9 Calories fats yield 194.0 

194.0 X 100 

Out of 100 Calories fats yield = 99 Calories 

195-9 
Tables II and VIII give for foods of vegetable and of animal 
origin, respectively, the content of the most important ash con- 
stituents, the foods being compared on the basis of equal fuel 
value. Table IV gives the average composition of lean and of 
fat meats of the same varieties. 



APPENDIX A 



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275 







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276 



APPENDIX A 



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277 







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278 



APPENDIX A 



TABLE II. — Foods of Vegetable Origin 

Important Ash Constituents in the One-hundred-Calorie Portion of 

Edible Material 1 



Fruits, Fresh 
Bananas ....... 

Grapes 

Plums 

Cherries 

Raspberries 

Pears 

Apples 

Oranges 

Lemons 

Peaches 

Strawberries 

Watermelons 

Fruits, Dried 

Dates 

Raisins 

Currants, Zante .... 

Figs 

Prunes 

Fruits, Specially Used 
For Pickles 

Olives, green 

Cucumbers 

As " Vegetables " 

Squashes 

Pumpkins 

Tomatoes 

Roots, Tubers, and Bulbs 

Sweet potatoes 

Potatoes 

Parsnips 

Onions 

Beets 



100- 
Calorie 
Portion 
(Edible) 



Grams 

101 
104 
118 
128 

151 
158 
159 
195 
226 
242 
269 
332 

29 
29 

31 
32 
33 



33 

575 

217 

389 
438 

81 
120 

154 
206 

217 



Important Ash Constituents 
Per ioo-Calorie Portion 



CaO 



Mg. 

10 
24 
29 
40 
no 

32 

22 
no 
120 

20 
130 

60 

30 
20 
40 

89 
20 



60 
120 

40 
no 

&7 

20 

19 
140 
120 

60 



P2O5 



Mg. 

55 
120 

64 

90 
180 
90 
5o 
90 
40 

113 

162 

60 



30 
80 
90 

99 

80 



10 
45o 

170 

420 

257 

80 
166 
290 
240 
190 



* Not determined. 
1 Selected from the more comprehensive tables of Sherman, " Chemistry of 
Food and Nutrition," pp. 338-341- 



APPENDIX A 



279 



TABLE II. — Foods of Vegetable Origin. — Continued 



Carrots 

Turnips 

Radishes 

Stalks and Leaves 

Cabbage 

Cauliflower 

Spinach 

Asparagus 

Rhubarb 

Lettuce 

Celery 

Legumes, Green 

Peas 

Beans, string . . . . 

Legumes, Ripe 

Peas 

Beans 

Fungi 
Mushrooms 

Cereal Products 

Oatmeal 

Cornmeal 

Barley, pearled . . . . 

Rice 

Rye flour 

Wheat flour, Graham 
Wheat flour, white . . 
Bread, Graham . . . 

Bread, white 

Bread, "whole wheat" . 

Nuts 

Walnuts 

Almonds 

Peanuts 

Chestnuts 



100- 
Calorie 
Portion 
(Edible) 



Grams 
221 
254 
341 

317 
328 

417 
4SO 

433 
525 
542 

100 
241 

28 
29 

223 

25 
28 
28 

29 
29 
28 
28 
38 
38 
4i 

14 
15 
18 

4i 



Important Ash Constituents 
Per ioo-Calorle Portion 



CaO 



Mg. 

168 
222 
170 

214 

550 
370 
170 
260 
260 
540 

32 
177 

40 
63 

53 



4 

7 

3 

5 

17 

7 

19 

11 

16 

IS 
46 
18 
17 



P2O5 



Mg. 

220 
292 

300 

280 

45o 
540 
390 
300 
470 
540 

240 
284 

250 
326 

530 

216 

80 
127 

57 
220 

253 

50 

190 

75 
160 

108 
132 
160 



Fe 



Mg. 

1.6 

i-3 
2.0 



3-5 

* 

13-3 

4-3 
* 

5.o 
2.7 



1.6 
3-8 

i-5 
2.0 



0.9 

0.3 

0.4 

°-3 

* 

i-5 

0.4 

i-3 
o-3 
0.6 



0.3 
0.3 

0.4 
0.4 



* Not determined. 



280 



APPENDIX A 



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APPENDIX A 



281 









































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282 



APPENDIX A 









































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Ah 






pq 


pp 








> 







APPENDIX A 



283 



vO t>- vO N» fO 

io 10 in 10 "1 



N O vo no O ^ to^O MD 

IO tO "t "t fO tn <NM 



O a rOO Tt" lO On 



U 



rf PO ^ PO N 
<* rf ■**■ ■* '*■ 



00 H 
^f vO 



IO Tf M 00 

10 m vo VO 



N» ^t" ^t O M N 

O N00 OO 00 00 



<t»0 V) H 

On On O On 



2Ph 



« M vo O *0 On 

S W) NOO M M 
S M M H <N CN 



VO vo O 'tf - PO H 00 TJ-rhOO 
CN po •t)- vo O w f) lOMD vO 

oi <n° cn <n oi 



O H t^- o O r~~ 

fOrotOtOro4't44 l n 1 n 



2t3 

-2 £3 



fe a 



« H 



O O O vo o 

ts N 0> t|- f3 
O 00 n n 



O O vo O O vo vo O O 10 vo o O vo vo O 

MOO -^•oou->m N vo •'d" PO O O vO <N MOO 



O 



fn 



s n 00 

*o • • 

. On <N 

5 M H 



PO 10 

6 On 



M VO H 

On NO 



n n 10 



O tOM N 

■4- d <>* h 



h 00 ro in to t|-o 
<N h h O O O O 



Ph 



SO O 00 00 00 
, rn n h r-- 00 

« CN (N Ol H H 



vO On <n NO PO^vOvO csvo N N CN vo <N 

06 <n 00606 O vo 00 O a NM 00 n vo rj- 

MtNMCNMHMHMHM 





PO vO vo O0 vO 


vo 00 vo Th 


^ N 


vo 


N N 


V 
u 


<N Tf PO O O 

vo no no n n 


M O CM PO 

n vO *>• n~ 


vo VO 


CO 
vo 


n~ vo 



<N M OO t-~ VO <N 

O On On h CM rt" 

N N NOO 00 OO 



Pi 



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PO 



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t^» H PO PN) 
rt vo vo vO 



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M 

J *o 



T3 g 

M 43 

03 03 

CO C/3 



a " p 

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cj ^ 43 
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rt 2 fe 

^ a ^ 

43 £^ 

^* 

J? TO 

en >_, 
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a 



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43 



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2 M 



tjO 



^ 



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fl 

"55 42 



'o 



03 

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u O tj cj 
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t3 

> 

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a 

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43 J2 

► •a 

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a; +-> 

44 S3 

h _2 

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43 O 

43 ^ 

en i-i 
cu cu 

^ I 

,2 



284 



APPENDIX A 



CA 

H 
O 
13 

Q 
O 
« 

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P4 

< 

Q 



0) 

> 

> 



O K 

I I 

o 

o a 

o 

CA O 

® 



0) 

> 



















t« 
















(U 




0- Calorie 
Portion 
• Measure 


1 glass 
asses 
asses 
sses 




C/3 
C/2 


in 
in 


c3 

HI 


^3 

• 1— 1 




?% 
h >a 


<tf 'Sb'Sb^ 




-3 


o3 


,r 3 

HI 


3 







g HINHN M 




~5b 


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O 


H|N 






CO H H (N 




lH|Td 


H|o0 


HI 


HI 




•St? 


a 


t^ r-~ 





(N 


O 


■^- OJ CO VO 






a >> 


K <N V/-> IV} t^ 


VO <N 








M 




a 



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4-J 


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VO 


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vo 


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fe 


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<N lO 


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On 


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fc 


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8 

















■*-> 


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10 


rj- 10 vio 


1— 1 
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Ph 
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8 

Ph 


V. M CO CO M 

■ft, 


H (N 






O 


N M t N 


■— j b4 














Ph 


03 O -, 

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2 HI O <N 


00 H 


M 


CO 


O 


t^ VJ-) \o cs 




s io 6\ d to 


q m 


CO 


O 


^r 


^°9 N . co 


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1 


M <N 


M 


O 


O 


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pq 

h- 1 


H O 
















C) 












Q 


Fuel 
Value 

per 
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.^ LO UO O O 


O w> 


O 


VO 


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W 


>> H \0 ^O IN 
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00 w> 


00 


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00 


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a 


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HI 


CO 


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8 * 


§ q h 00 q 


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q 




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4 


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1 


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oi 


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u 


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oj 


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H 


N 4 >0 ci 




£ 


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<N O 


«>- 


10 


HI 


cm co rt r^ 


Ph p 


per cent 










/— v +j 














• • 
















. 


-^ HI 
















<u ex 







eese, Cheddar 
eese, full- cream 
eese, skim-milk 
eese, cottage . 




Q 


& 


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x 2- 












Milk, whole . 
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sweetened) 
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"crj 


HI 

<u 

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14-1 


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W 


u u 




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UU U U 



APPENDIX A 



285 





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y Measu 






d 

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N 




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whites 
















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tn 

3 






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rt|N rtlMHC 












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a 


CN CN 


M to >0 




OOO 


O 


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e 



to 


1? >» 






CN CN M 
















O 




*-> 


8 


O « 


O -+ to 




CN CN O 


O 


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10 


vo 




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to <N 




.« 


fa 


K 


CN t-t 


CO CN M 




00 O 


O 


O 


to 


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fc 


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00 O 


O O to 




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H 


10 


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to 00 


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Fuel 
Value 

per 
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10 O O 


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153 

fa 




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co 6 6 


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w 

tyT 

c 






Fats 
tallow, n 


CD 

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id 

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286 



APPENDIX A 



TABLE VIII. — Foods of Animal Origin 

Important Ash Constituents in the One-hundred Calorie Portion 
of Edible Material x -v. 



Meats 

Bacon 

Ham ...... 

Beef, lean . . 
Veal, lean .... 

Chicken 

Frogs' flesh .... 

Fish 

Salmon 

Herring 

Halibut 

Pike . 

Haddock .... 
Cod 

Dairy Products 
Butter .' . . 

Cheese 

Cream 

Milk 

Buttermilk .... 

Eggs 

Whole 

Yolk 

White 



IOO- 

Calorie 
Portion 
(Edible) 



Grams 

16 

44 
5o 

65 
92 

153 



49 
70 

83 
123 

140 

150 



13 

22 

5o 

145 

280 



68 

28 
182 



Ash Constituents Per 
1 00- Calories 



CaO 



Mg. 

1 

5 

9 

12 

7 
42 



5 
5o 
10 
60 
40 
21 



3 

250 

70 

239 

4i5 



60 

So 
28 



P2O5 



40 
180 
420 
37o 
250 
670 



200 
380 
300 
600 
500 
600 



4 
329 
100 

303 
610 



240 

270 

5o 



Fe 



Mg. 

0.2 

1.1 

3-2 
* 

* 

* 



0.7 

* 

0.2 
* 

* 

0.6 



0.3 

* 



1.9 

2.3 

0.2 



* Not determined, 
^rom Sherman, Chemistry of Food and Nutrition, pp. 338-341. 



APPENDIX A 287 

TABLE IX. — Approximate Weights of One Cupful of 
Common Food Materials 

Ounces 

Almonds, shelled 5 

Baking powder 7 

Butter 8 

Beans-, dried , ". 12 

Chocolate, grated 3! 

Coconut, shredded 3 

Cocoa 4 

Coffee, ground 3 

Cornmeal . 5 

Currants, Zante 4f 

Farina 5! 

Figs, dried 4 

Flour, pastry, sifted 3! 

Flour, pastry, unsifted 4 

Flour, bread, sifted 4 

Flour, bread, unsifted 4! 

Gelatin 4 

Grape nuts 5 

Hominy 5! 

Lard 6j 

Lentils 6| 

Macaroni 4 

Milk 8| 

Molasses n| 

Oatmeal . 6f 

Oats, rolled 2\ 

Olive oil 7§ 

Peas, split 6| 

Prunes 6 

Raisins 4f 

Raisins, seeded $\ 

Rice 8 

Sugar, brown 4I 

Sugar, granulated 7 

Sugar, powdered $\ 

Sugar, icing 4! 

Sugar, loaf 4f 

Tea 2 

Tapioca (pearl) 6 

Walnuts, shelled 3 



APPENDIX B 
REAGENTS 

A mole, or gram-molecule, of a substance is the molecular weight 
in grams. 

An equivalent weight, or gram-equivalent, of a substance is the 
quantity which is chemically equivalent to one gram-atom (1.008 
grams) of hydrogen. 

A molar solution of any substance contains one mole of the 
substance per liter. A twice-molar solution (2 M) contains twice 
this quantity per liter, a half-molar solution (M/2) half the quan- 
tity per liter, and so on. 

A normal solution of any substance contains one equivalent 
weight of the substance per liter. A twice-normal solution (2 N) 
contains twice this quantity per liter, a half-normal solution one 
half this quantity per liter, and so on. 

Examples 

HC1 Molecular weight 36.5 

Mole 36.5 grams 

Equivalent weight 36.5 grams 

Molar solution (M) contains 36.5 grams hydrogen 
chloride gas per liter. This is also the normal solu- 
tion (N) of hydrogen chloride. 

A twice-molar solution (2 M, also 2 N) contains 73 
grams hydrogen chloride per liter. 
H2SO4 Molecular weight 98 

Mole 98 grams 

Equivalent weight 49 grams 

A molar solution of sulphuric acid contains 98 grams 
pure sulphuric acid per liter. This solution is twice- 
normal, 2 N. 

A half-molar (M/2) solution of sulphuric acid contains 
49 grams per liter. This is a normal solution. 



APPENDIX B 289 

Al2(S04)3 Molecular weight 342. 

Since there are two atoms of aluminium, each equiva- 
lent to three atoms of hydrogen, the mole of aluminium 
sulphate is equal to six equivalent weights. The 
equivalent weight is, therefore, 57. 

A molar solution (M) of aluminium sulphate is a six 
times normal (6 N) solution. 

A normal solution (N) is one-sixth molar (M/6). 



Reagents for General Use 

Acetic Acid, 2 N. Dilute 115 cc. glacial acetic acid to one liter. 

Alcohol. 95 per cent alcohol, or methylated spirits. 

Ammonium Chloride, 2 N. 107 grams to one liter. 

Ammonium Hydroxide, 5 N. Specific gravity 0.96. Dilute 
340 cc. concentrated ammonium hydroxide (sp. gr. 0.90) to one 
liter. 

Ammonium Oxalate, N/2 (M/4). 35 grams crystals, 
(NH 4 )2C 2 04 . H 2 0, to one liter. 

Barium Chloride, N (M/2). 122 grams crystals, BaCl 2 . 2 H 2 0, 
to one liter. 

Benzine. Commercial. 

Calcium Chloride, N (M/2). 56 grams anhydrous calcium 
chloride or no grams crystals, CaCl 2 . 6 H 2 0, to one liter. 

Calcium Hydroxide, Saturated. Slake a lump of quicklime, 
weighing about half a pound, by pouring upon it as much warm 
water as it will absorb and allowing it to stand for about ten min- 
utes. Put the slaked lime in a two-liter bottle, fill the bottle with 
distilled water, and shake well, allow to settle, and decant the clear 
liquid. By refilling the bottle with water many batches of lime- 
water may be prepared from the same portion of lime. 

Calcium Sulphate, Saturated. About 2.5 grams crystals, 
CaSC>4 . 2 H 2 0, to one liter. 

Copper Sulphate, N/2 (M/4). 62 grams crystals, CuS0 4 . 5 H 2 0, 
to one liter. 

Ether. 

Fehling-Benedict Solution. 
17.3 grams copper sulphate crystals, CuS0 4 . 5 H 2 
173 grams sodium citrate I to one 

100 grams sodium carbonate, anhydrous, or 270 grams liter 
sodium carbonate crystals, Na 2 C03 . 10 H 2 
u 



290 APPENDIX B 

Ferric Chloride, N (M/3). 90 grams crystals, FeCl3 . 6 H 2 0, to 
one liter. 

Hydrochloric Acid, Concentrated. About 13 N. Specific gravity 
1.20. 

Hydrochloric Acid, Dilute, 2 N. Specific gravity 1.035. Dilute 
170 cc. concentrated hydrochloric acid to one liter. 

Iodine. 20 grams potassium iodide 1 to one 
1 gram iodine J liter 

Lead Acetate, N (M/2). 190 grams crystals, Pb(C 2 H30 2 )2 . 3 H 2 0, 
to one liter. 

Litmus. Heat 10 grams commercial cubes with about 200 cc. 
water. Filter. Wash the residue several times with hot water. 
Make up to one liter. 

Magnesium Chloride, N (M/2). 102 grams crystals, 
MgCl 2 . 6 H 2 0, to one liter. 

Mercuric Chloride, N/5 (M/io). 27 grams to one liter. 

Millon's Reagent. Treat mercury with twice its weight of 
concentrated nitric acid (in a porcelain dish under the hood). 
Warm gently towards the last. When all is dissolved, add the 
liquid to twice its volume of water. Allow to settle a few hours 
and decant the clear liquid. 

Nitric Acid, Concentrated. About 16 N. Specific gravity 1.42. 

Nitric Acid, Dilute, 2 N. Specific gravity 1.065. Dilute 
130 cc. concentrated nitric acid to one liter. 

Phenolphthalein. 5 grams in one liter of alcohol (or of 60 per 
cent alcohol). 

Potassium Ferrocyanide, N (M/4). 106 grams crystals, 
K 4 Fe(CN) 6 . 3 H 2 0, to one liter. 

Potassium Hydroxide, 50 per cent. 770 grams to one liter. 

Potassium Iodide, N/5. 33 grams to one liter. 

Potassium Permanganate, M/io. 16 grams to one liter. 

Silver Nitrate, N/10. 17 grams to one liter. 

Soap. Shave 50 grams white castile soap. Dissolve in one 
liter hot water and filter. 

Sodium Carbonate, N(M/2). 53 grams anhydrous, or 143 
grams crystals, Na 2 CC>3 . 10 H 2 0, per liter. 

Sodium Hydroxide, 30 per cent. 400 grams to one liter. 

Sodium Hydroxide, 2 N. About 85 grams sodium hydroxide 
sticks to one liter. 

Sodium Phosphate, N (M/3). 119 grams crystals 
Na 2 HP0 4 . 1 2 H 2 to one liter. 



APPENDIX B 291 

Sulphuric Acid, Concentrated. About 36N(i8M). Specific 
gravity 1.84. 

Sulphuric Acid, Dilute, 2 N. Specific gravity 1.065. Dilute 
59 cc. concentrated sulphuric acid to one liter. 

Reagents for Special Use 

Acetic Acid, N. Experiments 62 and 63. Dilute the reagent 
acetic acid to twice its volume; or dilute 57.1 cc. glacial acetic 
acid to one liter. 

Aluminium Chloride, N/2 (M/6). Experiment 57. 22 grams 
crystals, AICI3 . 6 H2O, to one liter. 

Barium Acetate, N/2 (M/4). Experiment 57. 62 grams crys- 
tals, Ba(C2H 3 C>2)2 • H 2 0, to one liter. 

Barium Nitrate, N/2 (M/4). Experiment 57. 65 grams to one 
liter. 

Bleaching Powder. Experiments 155-160. Grind 100 grams 
bleaching powder in a mortar and gradually add about 50 cc. 
water, so as to form a paste. Add 250 cc. water, mix thoroughly, 
and filter. 

Calcium Bicarbonate (Artificial Hard Water). Experiments 69- 
71. Dilute limewater with an equal volume of distilled water. 
Pass in carbon dioxide until the precipitate formed at first is re- 
dissolved. If a little precipitate persists, filter the liquid. 

Chromic Sulphate, N/2 (M/12). Experiment 151. 60 grams 
crystals, C^SO^. 18 H 2 0, to one liter. 

Copper Sulphate for Fehling's Solution. Experiment 98. 17.3 
grams crystals, CuSC>4 . 5 H 2 0, to one liter. 

Cyanin. Experiment 148. 0.1 gram in a mixture of 50 cc. al- 
cohol and 50 cc. water. 

Eisner's Reagent (Basic Zinc Chloride). Experiment 132. 
500 grams zinc chloride 

20 grams zinc oxide 
425 cc. water 

Warm until clear. 

Ferrous Sulphate, N/2 (M/4). Experiment 151. 70 grams 
crystals, FeS0 4 . 7 H 2 0, to one liter. 

Formic Acid, Concentrated. About 36.5 N. Experiment $$. Spe- 
cific gravity 1.22. 

Formic Acid, N. Experiments 62 and 63. Dilute 37.7 cc. pure 
formic acid (sp. gr. 1.22) to one liter; or dilute 173.6 cc. formic 
acid of sp. gr. 1.06 to one liter. 



292 APPENDIX B 

Hydrochloric Acid, N. Experiments 62 and 63. Dilute the 
reagent dilute (2 N) hydrochloric acid to twice its original volume. 

Hydrochloric Acid, 3 per cent. Experiments 144, 146, 149. 
Dilute 400 cc. of the reagent dilute (2 N) hydrochloric acid to 
one liter. 

Hydrochloric Acid, 0.4 per cent. Experiment 116. 55 cc. 
dilute (2 N) hydrochloric acid to one liter. 

Indigo Carmine. Experiment 164. 1 gram indigo carmine to 
one liter. 

Lowe's Reagent. Experiment 154. Dissolve 25 grams copper 
sulphate and 12 cc. gylcerol in 250 cc. water. Add just sufficient 
sodium hydroxide solution to redissolve the precipitate formed. 

Oxalic Acid, Saturated. 120 grams crystals, H2C2O4 . 2 H 2 0, 
to one liter. 

Oxalic Acid, 5 per cent. Experiments 146 and 149. 50 grams 
crystals H2C2O4 . 2 H 2 to one liter. 

Pepsin. Experiment 116. 0.1 gram commercial dry pepsin 
to one liter. 

Potassium Chloride, N/2. Experiment 57. 37 grams to one 
liter. 

Potassium Bichromate, N (M/6). Experiment 169. 49 grams 
to one liter. 

Potassium Hydroxide, 30 per cent. Experiment 32. 385 
grams to one liter. 

Potassium Hydroxide, 5 per cent. Experiment 153. 50 grams 
to one liter ; or dilute the 50 per cent solution to 1 5 times its 
volume. 

Potassium Hydroxide in Alcohol. Experiment 82. 100 grams 
to one liter alcohol. 

Potassium Sulphate, N/2 (M/4). Experiment 57. 44 grams to 
one liter. 

Richardson's Reagent. Experiment 154. Dissolve 25 grams 
nickel sulphate crystals, NiS0 4 . 7 H 2 0, in 500 cc. hot water. 
Precipitate with sodium hydroxide solution. Wash thoroughly 
by settling and decantation. Dissolve in 125 cc. concentrated 
ammonia (sp. gr. 0.90) and make up to 250 cc. with water. 

Rosolic Acid. Experiment 147. 0.5 gram in a mixture of 50 cc. 
alcohol and 50 cc. water. 

Silver Sulphate, Saturated. 7 grams to one liter. 

Sodium Bisulphite, 30 per cent. Experiment 168. 385 grams 
to one liter. 

Sodium Bisulphite, M. Experiments 157, 158, and 164. 104 



APPENDIX B 293 

grams to one liter ; or dilute the 30 per cent solution to three 
times its volume. 

Sodium Carbonate, 1 per cent. Experiment 116 and 144. 
10 grams anhydrous sodium carbonate to one liter ; or dilute the 
reagent N. sodium carbonate solution to five times its volume. 

Sodium Carbonate, 0.05 per cent. Experiment 153. Dilute the 
reagent sodium carbonate to 100 times its volume. 

Sodium Chloride, 5 per cent. Experiments 57 and 109. 50 
grams to one liter. 

Sodium Citrate. Experiment 98. 173 grams to one liter. 

Sodium Sulphate, N/2 (M/4). Experiment 57. 80 grams 
crystals, Na 2 S0 4 . 10 H 2 0, to one liter. 

Sodium Potassium Tartrate for Fehling's Solution. Experiment 
98. 346 grams crystals, NaKC4H 4 06 . 4 H2O, to one liter. 

Sodium Thiosulphate, M./2. Experiment 157. 124 grams 
crystals, Na 2 S203 . 5 H 2 0, to one liter. 

Trypsin. Experiment 116. 0.1 gram commercial dry trypsin 
to one liter. 



APPENDIX C 
THE METRIC SYSTEM 
Meanings of the Prefixes 

Milli- = one-thousandth, .001. Compare mill = one one- 
thousandth of a dollar. 

Centi- = one-hundredth, .01. Compare cent = one one- 
hundredth of a dollar. 

Deci- = tenth, .1. Compare dime = one tenth of a dollar. 

Deca- = ten, 10. Compare decalogue = ten commandments. 

Hecto- = one hundred, 100. Compare hectograph = a gelatin 
pad for multiplying copies of a writing or drawing. 

Kilo- = one thousand, 1000. 

Length 

10 millimeters (mm.) = 1 centimeter (cm.) 
10 centimeters = 1 decimeter (dm.) 

10 decimeters = 1 meter (m.) 

1000 meters = 1 kilometer (km ) 

Area 

100 square millimeters (mm. 2 ) = 1 square centimeter (cm. 2 ) 
100 square centimeters = 1 square decimeter (dm. 2 ) 

100 square decimeters = 1 square meter (or centare)(m. 2 ) 

100 square meters = 1 are (a.) 

100 ares = 1 hectare (ha.) 

Volume (Capacity) 

1000 cubic millimeters (mm. 3 ) = 1 cubic centimeter (cm. 3 or cc.) 
1000 cubic centimeters 

(milliliters) = 1 liter 
1000 liters = 1 cubic meter (or stere) (m. 3 ) 

294 



APPENDIX C 



295 



Weight 

10 milligrams (mg.) = 1 

10 centigrams = 1 

10 decigrams = 1 

1000 grams = 1 

1 gram is the weight of 1 cubic centimeter of water at 4° 
1 kilogram is the weight of 1 liter of water at 4 C. 



centigram (eg.) 
decigram (dg.) 
gram (g.) 
kilogram (kg.) 



TABLES OF EQUIVALENTS 



1 millimeter 
1 centimeter 
1 decimeter 
1 meter 
1 kilometer 

1 inch 
1 foot 
1 yard 
1 mile 



Length 



.0394 inch 
.394 inch 
3.94 inches 
39.37 inches 
.62 mile 

2.54 centimeters 
3.05 decimeters 
9.15 decimeters 
1. 61 kilometers 



about -fa inch 
about f inch 
nearly 4 inches 
about itu yards 
about f mile 

about 2\ centimeters 
about 30 centimeters 
about ti meter 
about if kilometers 



Area 

1 centare (square meter) =1550 square inches = about 13 
square yards. 

1 hectare = 2.47 acres = nearly 2\ acres. 



Volume 



1 cubic centimeter (milliliter) 
10 cubic centimeters (1 centiliter) 
100 cubic centimeters (1 deciliter) 
1 liter 
1 cubic inch 



.06 cubic inch 

.61 cubic inch 

6.10 cubic inches 

61.03 cubic inches 

16.39 cubic centimeters 



296 APPENDIX C 

Capacity 

1. Dry Measure 

1 liter = .908 quart 

1 hectoliter = 2.84 bushels 
1 quart =1.10 liters 
1 gallon = 4.40 liters 
1 bushel = .35 hectoliter 

2. United States Liquid Measure (Wine Measure) 

1 liter = 1.057 quarts 

1 fluid ounce = xe pint = 29.6 cubic centimeters 

1 quart = .946 liter 

1 gallon =3-79 liters 

1 United States gallon = 231 cubic inches = almost exactly 
the capacity of a cylinder 7 inches in internal diameter and 6 inches 
in height. 

3. British Imperial Liquid Measure 

1 liter = .881 quart = about if pints 

1 fluid ounce = 2V pint = 28.4 cubic centimeters 
1 quart = 1.135 liters 

1 gallon = 4.54 liters 

1 Imperial gallon = 277.274 cubic inches = the volume of 10 
pounds of water at 62 F. (about 16 C). 

Weight 

1 gram = 15.43 grains 

1 kilogram = 2.20 pounds 

1 ounce Avoirdupois = 437.5 grains = 28.4 grams 

1 pound Avoirdupois = 7000 grains = 453.6 grams 



INDEX 



All acids are indexed under the word "acid," all alcohols under the word 
: alcohol," all enzymes under the word "ferments," and all oils under the word " oil." 



Absorption of food, 201 

Acetone, 167 

Acetylene, 78 

Acid, acetic, 85, 86, 114, 115, 116 
140; boracic, see boric; boric 
40, 234 ; butyric, 85 ; carbolic, 60 
234, 256; carbonic, 5, 122; citric 
85 ; ferrocyanic, 261 ; formic, 49 
50, 114, 116; hippuric, 194; hydro 
chloric, 84, 114, 115, 116, 228, 232 
245, 261 ; hydrofluoric, 84, 228 
hypochlorous, 244, 245 ; lactic, 85 
malic, 85; nitric, 84, 86, 87, 232 
nitrous, 258; oleic, 115, 119, 139 
141; oxalic, 113; palmitic, 115 
119, 139, 140; phosphoric, 199 
phytic, 199 ; rosolic, 237 ; salicylic 
234; stearic, 115, 119, 139, 140 
sulphurous, 244, 245-251 ; tannic 
264; tartaric, 85, 87 

Acid anhydrides, 169 

Acid radicles, 86, 88 

Acid salts, 88 

Acids, 82-85, 86; amino, 182-184, 
188; effect on litmus, 82, 84; fatty, 
139, 264; in metal polishes, 107; 
ionization of, 103, 116; organic, 
84, 140; reaction with alcohols, 
138, 139; reaction with bases and 
basic oxides, 98-100; reaction with 
metals, 82-85 ; strong and weak, 115 

Acrolein, 146 

Air, 24, 80 

Alanine, 183, 184 

Albuminoids, 188, 191 

Albumins, 188 

Alcohol, amyl, 134; butyl, 134; de- 
natured, 67 ; ethyl, 67, 134, 136 ; 
grain, 67, 134, 138; methyl, 67, 
134, 137; propyl, 134; wood, 67, 134 



Aldehydes, 167 

Aldoses, 166-167 

Alizarin, 256, 263, 264 

Alkali, free, in soaps, 120, 148, 149, 
222—223; volatile, 131 

Alkali blue, 252 

Alkalies, 91-93 ; caustic, 93 ; strong, 
93 ; mild, 93 ; weak, 93 ; fixed, 131 ; 
volatile, 130 

Alkaloids, 182 

Alkanet, 256 

Almond paste, 276 

Almonds, 276, 279, 287 

Aluminium, injured by free alkali, 148 ; 
mordants, 263, 264 ; polish for, 108 ; 
tarnish of, 105 ; valence of, 88 

Amides, 182 

Amines, 183 

Amino acids, 182-184, 188, 213 

Amino radicle, 183, 257 

Ammonia, 127-131, 183, 223; an- 
hydrous, 128; "crystal," 131; 
"household," 130; in metal polishes, 
107; liquid, 128; " solid household, " 

131 
Ammonium radicle and salts, 130-13 1 
Amyl, 132 
Amyl acetate, 138 
Amylopsin, 176, 204, 206 
Analysis, chemical, 24 
Anhydrides, acid, 169 
Aniline, 135, 183, 256, 260; aniline 

dyes, 256 ; aniline black, 260-261 
Anion, 103 
Anthracene, 256 
Anthracite, 64 

Antimony, use in dyeing, 265-266 
Apples, 210, 271, 278 
Aqua ammoniae, 127 
Archil, 256 



297 



298 



INDEX 



Arrowroot, 177, 273 

Asbestos, 3 

Ashes, 59, 61, 64, 65; coal, 64; wood, 

61-62 ; of foods, 163-164, 193, 

278-279, 286; of silk, 228 
Asparagine, 182 
Atomic weights, 31, 33 
Atoms, 29-33 

Bacon, 142, 280, 286 

Baking powder, 35-37, 287 

Bananas, 207, 268, 269, 271, 278 

Barley, 274, 279 

Bases, definition, 94, 130; reaction 
with acids, 98-100; ionization of, 
103, 116; relation to basic oxides, 
95-96; strong and weak, 115 

Basic oxides, 95, 96; reaction with 
acids, 100 

Bass, 283 

Beans, 210, 212, 217, 273, 279, 287 

Beef, 214, 217, 281, 282, 286 

Beets, 210, 272, 278 

Benzaldehyde, 167 

Benzene, 159, 160, 256 

Benzine, 57, 66, 133, 159, 160, 161 

Beriberi, 199 

Bile, 160, 199, 204 

Biuret, 187 

Blackfish, 283 

Bleaching, 243-251 ; by hydrogen 
peroxide, 248, 251 ; by oxidation, 
243 ; by potassium permanganate, 
249 ; by sodium hypochlorite, 247 ; 
by sodium perborate, 249 ; by sul- 
phurous acid, 244 ; by sunlight, 243, 
249 ; grass, 243, 246, 249 ; of cotton 
and linen, 246 ; of feathers, 248 ; 
of ivory, 248; of silk and wool, 

251 _ 
Bleaching powder, 244-247 
Blood, 193, 199, 201 
Blueing, 251-253 
Bones, 193 

Borax, 92, 124, 223; in soap, 153 
Bran, 199 

Brass, 106, 107, 108 
Bread, composition and nutritive value, 

211, 275, 279; formation of dextrin 

in, 179; raising of, 175 
British thermal unit, 52 
Bronze, 106, 107 



Burner, Argand, 79; Bunsen, 2, 79; 

Tirrill, 3 
Butter, 139, 141, 284, 286, 287; cocoa, 

209; peanut, 276 
Butter crackers, 275 
Buttermilk, 213, 215, 284, 286 
Butternuts, 210, 276 
Butyl, 132 

Cabbage, 272, 279 

Caffein, 182 

Cakes, 275 

Calcium, 18; as a food constituent, 
193, 211, 212, 216, 217; excretion 
of, in feces, 194; in animal foods, 
216, 217; in vegetable foods, 211, 
212; ion in hard water, 121; ion, 
reaction with soap, 121; valence 
of, 87 

Calcium bicarbonate in hard water, 
122-125 

Calcium carbonate, 14, 29-30; rela- 
tion to hardness of water, 122—125 

Calcium chloride, 234 

Calcium hydroxide, 93, 96 

Calcium hypochlorite, 243, 244-247 

Calcium oxide, 14, 96 

Calcium phosphate in bones, 193 

Calcium sulphate, relation to hardness 
of water, 122-125 

Calico printing, 266 

Calomel, 88 

Calorie, definition of, 52 

Calorimeters, 52, 55; animal, 195; 
respiration, 195-196 

Candles, 75, 76; experiments with, 
43-46 

Caramel, 181 

Carbohydrates, 162, 164, 166-181 ; 
classification of, 168; composition 
of, 165; diffusibility of, 201-203; 
fuel value of, 197 ; hydrolysis of, 
166, 171-172, 203; oxidation prod- 
ucts of, 194; prominence in vege- 
table foods, 209 ; rarity in animal 
foods, 213 

Carbon, 17, 18; an element of fuels, 
59; an element of limestone, 19; 
combustion of, 16, 17, 46; filaments 
in electric lighting, 80-81 ; in lumi- 
nous flames, 77 ; in organic com- 
pounds, 132 



INDEX 



299 



Carbonizing, 221 

Carbon dioxide, formula of, 27, 29, 38; 
limewater test for, 5 ; production 
from limestone. 18, 29—30; produc- 
tion in combustion, 17, 46-47; pro- 
duction in the body, 194; produc- 
tion from marble, 13-14; production 
in yeast fermentation, 5 ; reduction 
to monoxide, 48 

Carbon monoxide, formula of, 27, 29, 
38; formation and properties, 47- 
50; in coal gas and water gas, 59, 63 

Carbon tetrachloride, 160, 161 

Carboxyl radicle, 140, 183 

Carrots, 210, 272, 279 

Casein, 184, 185, 216, 238 

Caseinogen, 185 

Catechu, 226, 265 

Cation, 103 

Cauliflower, 212, 273, 279 

Celery, 212, 273, 279 

Cellulose, 168, 170, 172, 180, 209, 
229-232 ; behavior in digestion, 
180; esters of, 232; hydration of 
in mercerizing, 234 ; in textile fibers, 
229, 231-234, 237; in vegetable 
foods, 209 ; nitration of, 232 ; solvents 
for, 231—232, 238-240 

Cereals, 200, 212, 273-275, 279 

Cejium, 79 

Chalk, 122; French, 160 

Charcoal, see also carbon, 41 ; as fuel, 
59, 64 

Chardonnet artificial silk, 239 

Cheese, 213, 215, 284, 286 

Chemical changes, 4, 9, 27, 30 

Chemicking, 246 

Chemistry, subject matter of, 1, 2, 9, 
10, 24 

Cherries, 271, 278 

Chestnuts, 276, 279 

Chicken, 281, 286 

Children, foods suitable for, 212, 217 

Chloride of lime, see bleaching powder 

Chlorine, 18, 19, 21, 88, 244, 245 

Chloroform, 160 

Chocolate, 209, 211, 276, 287 

Cholesterol, 220 

Chrome yellow, 255 

Chromium oxide, 255 

Cider, 5 

Citrons, 271 



Clams, 213, 285 

Clay, china, 234 

Coal, 42, 59, 62-65 

Coal oil, 66 

Cochineal, 256 

Cocoa, 210, 211, 276, 287 

Cocoa butter, 209 

Coconuts, 276, 287 

Cod, 215, 283, 286 

Coffee, 287 

Coke, 41, 59, 64, 68 

Collagen, 191 

Collodion, 233, 239 

Colloids, 178, 201, 203 

Compounds, 22-25, 38; nomenclature 
of, 25, 39 

Conduction of electricity, 20, 100; of 
heat, 20 

Cookies, 275 

Combination, 11, 15-17 

Combustion, 41-58; heat of, 54; im- 
portance of, 41; of charcoal, 16, 
17; products of incomplete, 47; 
products of, 8, 46-47 ; propagation 
of, 56 ; relation to heat, 51-58 ; spon- 
taneous, 57—58; surface, 71 

Copper, 16, 106; alloys of, 106; car- 
bonate, 106; hydroxides, 94, 95, 
170; oxides, 39, 95, 169; sulphate, 
243 ; tarnishing of, 106 

Cornmeal, 274, 279, 287 

Corrosive sublimate, 88 

Cotton, 229-235; as typical cellulose, 
170, 171, 180, 231 ; boiling-off of, 
230; distinction from linen, 236- 
238; dyeing, 257; fibers, 230; 
mercerization of, 233 ; mercerized, 
distinction from silk and lustra- 
cellulose, 241 ; plant, 229 ; printing, 
266 ; separation from silk and wool, 
241 ; sizing of, 234 ; use in gas 
mantles, 79 

Crackers, 275 

Cream, 213, 215 

Cream of tartar, see potassium bi- 
tartrate 

Creatine, 182 

Creatinine, 182, 194 

Cresols, 234, 256 

Crystalloids, 178, 203 

Cucumbers, 272, 278 

Cudbear, 256 



3°° 



INDEX 



Cuprammonium, or cuprate, artificial 

silk, 239 
Cupric hydroxide, 95 
Cupric oxide, 95 
Cuprous oxide, 39, 95, 169 
Currants, red, 180; Zante, 271, 278, 287 
Cutch, 226 
Cyanogen, 74 

Dairy products, 284, 286 

Dalton, John, 28 

Dandelion greens, 272 

Dates, 268, 271, 278 

Decay, 15 

Decomposition, n, 14, 15, 18, 28; of 

proteins, 185 
Definite proportions, law of, 34 
Deflagrating spoon, 54 
Dextrin, 168, 172, 179, 234 
Dextrose, see glucose 
Diamond, 53 
Diazonium salts, 258, 262 
Diazotizing, 258 
Dietary standards, 210, 211 
Digestion, 201-206 
Digestive fluids, 204 
Disaccharides, 168, 171, 172, 175-177, 

203 
Doughnuts, 274 

Dressing of cotton goods, 234-235 
Dressing of linen goods, 238 
Dry-cleaning, 160, 161 
Dunging, 263 
Dyeing, 254-266 
Dyes, acid, 257, 265 ; adjective, 255 ; 

aniline, 256 ; basic, 257, 265 ; 

"bleeding" of, 257; coal-tar, 256; 

developed, 257, 259—262 ; direct, 

257 ; inorganic, 255 ; natural, 255 ; 

organic, 255; mordant, 255, 257, 

263-264; substantive, 255, 257-259; 

sulphur, 259 ; synthetic, 256 ; vat, 259 

Edestin, 189 

Eels, 215, 283 

Eggs, 215, 217, 285, 286; albumin of, 
185, 186, 189; as food for children, 
217; ash constituents of, 217, 286; 
composition and nutritive value of, 
285; white of, coagulation of, 185, 
189, composition of, 200, 213, 215; 
yolk of, 191, 216 



Electric lighting, 80—81 

Electrolysis, 12, 13, 14, 101 

Electrolytes, 100—104 

Electrons, 32 

Elements, 18-21, 29, 32; symbols of, 

26, 3$ ; atomic weights of, 31, 33 
Emulsion, 159 
Enamelware, in 
Enzymes, see ferments 
Equations, 27 
Equivalent weight, 288 
Erepsin, 204 
Esters, 138-147 ; hydrolysis of, 143- 

144; saponification of, 144-145; 

"mixed," 141; of cellulose, 232 
Ethane, 133 
Ether, 159, 160 
Ethyl, 132 
Ethyl acetate, 138; structural formula 

of, 140 
Ethyl alcohol, 67, 134, 138 
Ethylamine, 183 
Explosion, 56, 57; of acetylene, 78; 

of kerosene lamps, 76-77 
Extractives of meat, 182 

Fabrics, the cleaning of, 160; see also 
fibers 

Farina, 287 

Fats, composition of, 165, 285; con- 
stitution of, 139-142 ; saponifica- 
tion of, 145-147 ; solvents for, 159- 
160; emulsification of, 159; as 
food constituents, 162-165 ; oxida- 
tion products of, 194 ; fuel value 
of, 197; digestion and absorption 
of, 203, 204 ; in vegetable foods, 211 ; 
in animal foods, 213—215; phos- 
phorized, 216; in cotton dressings, 
234; unsaponified, in soaps, 148-149 

Feces, 194, 197 

Fehling-Benedict solution, 169, 170 

Fehling's solution, 169, 170 

Fermentation, alcoholic, 5, 67, 175; 
digestive, 203—206 

Ferments, 143, 206; amylases, 176, 
178, 204; amylopsin, 204; diges- 
tive, 203 ; erepsin, 204 ; invertases, 
see sucrases; lactase, 177, 204; 
lipases, 143, 204; maltases, 176, 
204 ; nature of, 206 ; pectinase, 
235; pepsin, 185, 204, 205, 206; pro- 



INDEX 



301 



teases, 204, 205 ; ptyalin, 204, 205 ; 
rennin, 185 ; steapsin, 144, 204 ; 
sucrases, 175, 204; table of, 204; 
trypsin, 185, 204, 205; zymase, 175 

Ferric ferrocyanide, 226, 253 

Ferric hydroxide, 94, 95, no, 253, 255 

Ferric oxide, 95, 109-110, 255 

Fertilizer, 62 

Fiber, crude, 180 

Fibers, textile, 218—242; animal, 218- 
228; cotton, 229-235; effect of 
dyes upon, 254-255; hair, 218, 219; 
linen, 235—238; lustracellulose, 238- 
239; mineral, 218; silk, 223—228; 
vegetable; 229— 242 ; wool, 218-223 

Fibrin, 185, 205 

Fibrinogen, 185 

Fibroin, 223, 224 

Figs, 271, 278, 287 

Filberts, 276 

Fillers in soaps, 153 

Filter, folding, 6, 7 

Finishing of cotton goods, 234 

Fish, 215, 216, 283, 286 

Flame, 41, 42 

Flax, 235, 236, 237 

Flounder, 283 

Flour, wheat, 190, 210, 234, 274,279, 287; 
graham, 212, 274, 279; rye, 274, 279. 

Foods, absorption of, 201 ; animal, 
213-217, 280-286; as building 
material, 192 ; as fuel, 193 ; as 
physiological regulators, 198 ; baked, 
274-275 ; digestion of, 192-199 ; 
functions of, 192—199 ; general 
composition of, 162-165 ! vegetable, 
207-212, 271—279; weights of one 
cupful of common, 287 

Foodstuffs, inorganic, 162-164, I 93. 
199; organic, 162, 164,165, 166-199 

Formaldehyde, 167, 257, 259 

Formulas, 26, 27, 29; structural, 136 

"Fountain apparatus," 129 

Fowl, 281 

Frogs' legs, 216, 285, 286 

Fructose, 167, 168, 173, 213 

Fruit-juice, fermentation of, 5, 134; 
sugars of, 173 ; pectin of, 180 

Fruits, 175, 198, 200, 209, 271, 272, 278 

Fruit sugar, see fructose 

Fuels, 50-71 ; gaseous, 68-71 ; liquid, 
66-68; solid, 60-65 



Fuel values of nutrients, 197 
Fuller's earth, 160 
Fungi, 273, 279 
Fustic, 256 

Galactans, 174 

Galactose, 168, 174 

Gallnuts, 265 

Gas, acetylene, 77, 78; air, 70; Blau, 
71; coal, 42, 59, 68, 77 ; compressed, 
70; enrichment of, 70; gasoline, 
70, 77; illuminating, 42, 68—71, 
77-78; liquefied, 70; natural, 68, 
78; oil, 70, 77; water, 69-70, 78 

Gases, elementary, 19, 21 ; as fuels, 59 

Gas mantles, 75, 78 

Gasoline, 57. 66, 133, 159 

Gasoline gas, 70 

Gastric juice, 199, 204 

Gelatin, 184, 191, 213, 228, 234, 238, 
285, 287 ; silk, see sericin 

Germ of cereals, 211 

Glass, manipulation of, 3, 4, 5, 23 

Gliadin, 184, igo 

Globulins, 189 

Glucose, 168, 173; commercial, 173; 
fermentation of, by yeast, 5 ; in 
fruit juices, 5; in honey, 213; in 
silk- weighting, 227. 

Glue, 191, 228 

Glutelins, 190 

Gluten, 190 

Glutenin, 190 

Glycerin {see also glycerol), 147, 155, 234 

Glycerol, 135 ; an alcohol, 135 ; a 
product of soap making, 147 ; de- 
composition of, 146; structural for- 
mula of, 137 

Glyceryl radicle, 135 

Glyceryl oleate, see triolein 

Glyceryl palmitate, see tripalmitin 

Glyceryl stearate, see tristearin 

Glycine, 183, 184 

Glycogen, 168, 172, 179, 216 

Gold, 106 

Goldbeater's skin, 202, 203 

Goose, 281 

Gram-equivalent, 288 

Gram-molecule, 288 

Grape nuts, 287 

Grapes, 271, 278 

Graphite, 53, no 



302 



INDEX 



Grass bleaching, 243, 246 
Gums, 234 
Gun-cotton, 233 
Gypsum, 122, 234 

Haddock, 215, 283, 286 

Hair, 191, 218—219 

Halibut, 283, 286 

Ham, 280, 282, 286 

Hardness of water, 1 21-126 ; degrees of, 

125; permanent and temporary, 123 
Heat, 51-52; of combustion, 54-56; 

produced in chemical reactions, 9 ; 

production in the body, 193-198 ; 

units, 52 
Helium, 73 

Hemoglobin, 47, 184, 193, 216 
Hemp, 229 
Herring, 283, 286 
Hexoses, 167 
Hickory nuts, 276 
Hilum of starch granules, 178 
Hominy, 274, 287 
Honey, 166, 173, 213, 277, 285 
Horse-chestnut tannin, 265 
Human body, composition of, 192 
Hydrocarbon radicles, 132 
Hydrocarbons, 108, 133 
Hydrogen, 13, 18, 19, 21, 31, 37; an 

element of fuels, 59 ; as a product of 

electrolysis, 101 ; in acids, 84-86 ; 

ion, 103 
Hydrogen peroxide, 38, 243, 248-249, 251 
Hydrolysis, of salts, 117-119, 228; of 

esters, 143-145 ; of carbohydrates, 

171-172; of organic nutrients in 

digestion, 203-206; of starch, 172, 

173, 178; of stannic chloride in 

weighted silk, 228 
Hydroxides, 94 
Hydroxyl, 101, 103 
Hygroscopicity of cotton, 222, 238; 

of linen, 238; of silk, 224; of wool, 



Ice colors, 262 
Ignition temperature, 53 
Illumination, 72-81 
Incandescence, 43, 71-75, 78, 80 
Incandescent lights, 75, 79, 80 
Indigo, 250, 252, 253, 255-256, 259 
Indigo carmine, 250, 251, 252 



Intestinal juice, 204 

Intestines, absorption in, 201 ; diges- 
tion in, 204 

Inversion of sugar, 174 

Invertase, see sucrase 

Invert sugar, 174 

Ionization, 100-104, 116 

Ions, 102 

Iron, as an element, 19, 20, 22; cast, 
109; combination with sulphur, 22- 
23 ; effect of heating, 3, 4 ; excre- 
tion of in feces, 194 ; galvanized, 
in, 112; in animal foods, 216; in 
foods, 193, 211, 212, 216; in hemo- 
globin, 193, 216; in vegetable foods, 
211, 212; mold, 112; oxide, 100- 
110, 255; protection from corrosion, 
no— 112; rust, 109-113 ; rust stains, 
112-113: sulphide, 22, 23, 25; use 
in silk- weighting, 215-216; valence 
of, 88; wrought, 109 

Isinglass, 191 

Isomers, 136 

Japan, in 
Javel water, 247-248 
Jelly, 180, 181 
Jute, 229 

Keratins, 191, 218 
Kermes, 256 

Kerosene, 66, 76, 133, 160 
Ketoses, 166-167 
Khaki, 255 

Labarraque's solution, 248 
Lac dye, 256 
Lacquers, 108, in 
Lactase, 204 

Lactose, 168, 172, 176, 215 
Lakes, 263 
Lamb, 215, 280 
Lampblack, 75 
Lamps, 75, 77 
Lanolin, 220 
Lard, 139, 141, 285, 287 
Lead, tarnish of, 105 
"Lead," black, no; pencils, no 
Lecithin, 199 
Legumes, 212, 273, 279 
Legumin, 189 

Lemons, 271, 278; pectin of inner peel 
of, 180 



INDEX 



303 



Lentils, 287 

Lettuce, 273, 279 

Leuco compounds, 259 

Levulose, see fructose 

Light, 72; electric, 80; gas, 77 

Lignite, 62 

Lignocellulose, 180, 229 

Lime, acid phosphate of, 89 ; chloride 
of, 244; composition of, 18; in 
foods, see calcium; production from 
limestone, 13, 18; slaked, 93; slak- 
ing of, 14, 96 

Limelight, 78-79 

Limestone, as a cause of hardness of 
water, 122; decomposition of, 14, 
18, 29-30; elements of, 19 

Limewater, as reagent for carbon 
dioxide, 5 ; nature of, 14, 93 

Linen, 180, 229, 235-238; dressing of, 
238; fibers, 236; hygroscopicity 
of, 238; tests for, 236-238 

Lipase, 143, 204 

Liquor ammoniac, 127 

Litmus, 84 

Liver, 213, 281 

Lobsters, 285 

Logwood, 255 

Lustracellulose, 229, 238-241 

Lymph, 201 

Macaroni, 274, 287 

Macaroons, 274 

Mackerel, 283 

Madder, 256 

Magnesium, 3, 82, 87, 105 ; excretion 

of in feces, 194; ion in hard water, 

121 
Magnesium chloride, 227, 234 
Magnesium sulphate, 25 
Malt, 176 
Maltase, 204 
Malt extract, 176 
Maltose, 168, 172, 176, 177 
Manila, 229 

Marble, 122; decomposition of, 13-14 
Marl, 122 
Marmalade, 181 
Matches, 53, 54 
Matrass, 5 
Matter, 20; "mineral," in foods, 162, 

164 
Meat, ash-constituents of, 286; com- 



position of, 200, 213—215, 216, 280- 
282; extractives of, 182 

Mercerization of cotton, 233-234 

Mercuric chloride, 7, 232 

Mercuric oxide, n, 14 

Mercury, 14, 18, 19 

Metals, 20; polishing of, 107; polishes 
for, 108 ; relation to acids and salts, 
82-89 ; tarnishing of, 105—106 ; 
valences of, 87 

Methane, 59, 69, 133 

Methyl, 132 

Methylamine, 183 

Methyl butyrate, 138 

Metric system, 294 

Milk, as a food for children, 217; ash- 
constituents, 200, 286 ; calcium in, 
216, 286; carbohydrate of, 176, 
177, 213; coconut, 276, composi- 
tion and nutritive value, 284 ; con- 
densed, 215, 284; evaporated, 215, 
284 ; experiments with, 6, 7 ; phos- 
phorus in, 216, 286; powder, 215; 
skim, 213, 215, 284; weight of 
cupful, 287; whole, 215, 284 

Millon's test, 187 

Mineral matter, in coal, 64; in foods, 
161-163, 193, 198; in wood, 60; in 
wool, 220 

Mineral pigments, 255 

Mixtures, distinguished from com- 
pounds, 22 

Molar solution, 288 

Molasses, 277, 287 

Mole, 288 

Molecules, 28-31 

Monosaccharides, 166,168, 173-177, 203 

Mordants, 255, 263-264, 265, 266 

Mucins, 184 

Mushrooms, 210, 273, 279 

Mutton, 214, 280 

Naphthalene, 256 
Naphthol (£-), 258, 262 
Neutralization, 98 
Nicotine, 182 
Nickel, 106, in 
Nickelware, in, 112 
Nitrocellulose, 232, 239 
Nitrogen, 19, 21, 24, 59 
Nomenclature, 24, 25, 39, 86 
Non-metals, 20 



3°4 



INDEX 



Normal solution, 288 

Notation, chemical, 26, 27, 86-87 

Nucleins, 184 

Nutrients, elementary composition of, 
165; fuel values of, 197; in animal 
foods, 213-217; in vegetable foods, 
209-212; organic, 162, 164-199; 
oxidation products of, 194, 199 

Nuts, 209, 211, 276, 279 

Oatmeal, 209, 210, 211, 212, 273, 279, 

287 
Oats, rolled, 211, 273, 287 
Oil, castor, 139, 141, 155; coconut, 

155; cottonseed, 139, 150; lard, 

76, 139 ; linseed, 58, 139, 141 ; olive, 

76, 139, 150, 209, 264, 287 ; palmnut, 

I 5°» !55; pear, see amyl acetate; 

pineapple, see methyl butyrate; 

turkey-red, 161, 264; whale, 76 
Olein, see triolein 
Oleomargarine, 285 
Olives, 209, 211, 269, 272, 278 
Onions, 272, 278 
Oranges, 180, 210, 212, 271, 278 
Organic acids, 140; chemistry, 132; 

compounds, 132; radicles, 132 
Oxidation, in the body, 193-198, 199 ; 

in bleaching, 243 ; slow, 58 
Oxidizing agent, 243 
Oxgall, 160 
Oxycellulose, 246, 247 
Oxygen, 11, 13, 16, 17, 18, 19, 21, 24, 

25, 27, 88 
Oyster crackers, 275 
Oysters, 213, 285 
Ozone, 249 

Paint, as a protective coating for iron, 

in; drying of, 58 
Palmitin, see tripalmitin 
Pancreatic juice, 176, 204 
Paper, 229 
Paraffin, 66; hydrocarbons, 133; 

wax, 66, 76, no, 133 
Paranitraniline red, 262 
Parchment paper, 201, 202, 232 
Parsnips, 272, 278 
Peaches, 271, 278 
Peanuts, 210, 276, 279 
Pearl ash, 151 
Pears, 271, 278 



Peas, 210, 273, 279, 287 

Peat, 59, 62 

Pecans, 276 

Pectin, 168, 180, 209, 235, 237 

Pentoses, 167 

Pepsin, 185, 204, 205, 206 

Peptides, 183 

Peptones, 185 

Perch, 283 

Persian berry, 255 

Petrolatum, 66 

Petroleum, 66, 76, 77, 133, 153 

Phenolphthalein, 120 

Phenols, 256 

Phenylamine, see aniline 

Phosphorus, 20, 43-44, 53, 54; ex- 
cretion of, in feces, 194; in animal 
foods, 216, 217; in foods, 193, 199, 
211, 212, 216, 217; in proteins, 184, 
216; in vegetable foods, 211, 212 

Phosphorus pentasulphide, 53 

Physical change, 3, 9, 29-30 

Physical states, 20 

Pickerel, 215, 283 

Pickles, 272, 278 

Pies, 275 

Pike, 283, 286 

Platinum, 3, 106 

Plumbago, see graphite 

Plums, 271, 278 

Polypeptides, 183 

Polysaccharides, 168, 171, 172, 177-181, 
203 

Pork, 214, 215, 270, 280, 282 

Potash, see potassium carbonate ; 
caustic, see potassium hydroxide 

Potassium, 18, 20, 87 

Potassium binoxalate, 89, 113 

Potassium bisulphate, 89, 146 

Potassium bitartrate, 35-37, 89 

Potassium carbonate, in commercial 
soaps, 151, 157; in wood ashes, 
61-62 

Potassium chlorate, 11, 18, 29, 54 

Potassium chloride, 18, 29 

Potassium hydroxide, 93 

Potassium iodide, 7, 8 

Potassium permanganate, 243, 249, 250 

Potassium sodium tartrate, 35 

Potatoes, 209, 211, 272, 278 

Potatoes, sweet, 272, 278 

Poultry, 281, 286 



INDEX 



305 



Precipitate, 6 

Prefixes, signification of, 39, 294 

Prepares, 262 

Primuline, 258 

Printing of cotton, 266 

Propyl, 132 

Protein derivatives, 185 

Proteins, 162, 164, 182— 191 ; as body 
building material, 192-193 ; classes 
of, 184, 1 88-1 9 1 ; composition of, 
165; conjugated, 184; constitu- 
tion of, 183; derived, 184; diges- 
tion of, 203, 204; estimation of in 
foods, 182 ; fuel value of , 197 ; hydroly- 
sis of, 183, 184; importance in 
animal nutrition, 193 ; in animal 
foods, 213-216; in vegetable foods, 
210, 211; native, 184; origin of 
name, 193 ; oxidation products of, 
194-195; tests for, 185-187 

Proteoses, 185 

Prunes, 271, 278, 287 

Prussian blue, 226, 253 

Ptyalin, 176, 204, 205 

Pudding, tapioca, 275 

Pumpkins, 210, 272, 278 

Putty powder, 107 

Pyroxylin, 233, 239 

Quercitrin bark, 255 

Quicklime, see lime and calcium oxide 

Quinine, 182 

Radicals, see radicles 

Radicles, acid, 86; amino, 183; am- 
monium, 130; amyl, 132; butyl, 
132 ; carboxyl, 140, 183 ; ethyl, 
132 ; glyceryl, 135 ; hydrocarbon, 
132 ; hydroxy 1, 101 ; organic, 132- 
137; propyl, 132; sulphate, 101 ; 
valence of acid, 88 

Radioactivity, 19, 32 

Radishes, 209, 210, 272, 279 

Raisins, 271, 278, 287 

Ramie, 79, 229 

Raspberries, 271, 278 

Reagents, 288-293 

Reducing agent, 244 

Reducing sugars, 170 

Reduction, 49, 169, 244 

Refuse of foods, 207, 215 

Retting of flax, 235 



Rhubarb, 273, 279 

Rice, 274, 279, 287 

Rolls, 275 

Roots, 212, 272, 278—279 

Rosin, 152 

Rottenstone, 107 

Rouge, 107 

Rust, 109-113; stains, n 2-1 13 

Saccharose, see sucrose 

Sago, 177, 277 

Saliva, 176, 199, 204 

Salmon, 215, 283, 286 

Salt, common, see sodium chloride; 
Epsom, see magnesium sulphate ; 
Glauber's, see sodium sulphate; 
of sorrel, see potassium binoxalate; 
of lemons, see potassium binoxalate ; 
Rochelle, see potassium sodium 
tartrate; smelling, 131 

Salt colors, 256 

Saltpeter, 22 

Salts, see also salt ; acid, 88 ; defini- 
tion of, 86; hydrolysis of, 11 7-1 19; 
nomenclature and notation of, 86; 
reactions to litmus, 118-119; re- 
lation to acids and bases, 99 ; relation 
to acids and metals, 85 

Sandalwood, 256 

Saponification, 144-145 

Sardines, 215, 283 

Science, 1 

Scleroproteins, 191 

Scouring powders, 148, 156 

Sericin, 223, 224 

Shad, 215, 283 

Shad roe, 213, 216, 285 

Shellac, 108 

Shellfish, 213, 216, 285 

Silk, 223-238; artificial, 229; boiled- 
off, 224; degumming of, 224; dis- 
tinction from wool, 191; ecru, 224; 
origin of, 223 ; pongee, 223; "pure," 
227; separation from wool, 225; 
separation from cotton, 241—242 ; 
souple, 224; solvents of, 225, 242; 
weighting, 225-228; wild, 223 

Silkworms, 223, 238—241 

Silver, 106, 107, 108 

Silver chloride, 6, 27, 31 

Silver nitrate, 6, 27, 31, 35 

Silverware, 106 



306 



INDEX 



Sirup, corn, 173; glucose, 173; maple, 

277 

Sisal, 229 

Sizing of cotton, 234 

Smelt, 283 

Smoke, 59 ; oil of, 60 

Soap bark, 160 

Soap powders, 156 

Soaps, as emulsifying agents, 158-159; 
calcium, 121; carbonates in, 151; 
colored, 155; commercial, 148—157; 
curd, 147; detergent effect of, 159; 
effect of water upon, 119; effect of 
hard water upon, 121, 125; fillers in, 
153; floating, 155; for woolens, 
222, 223; free alkali in, 120, 148, 
149; hard, 119, 147, 150; hydrolysis 
of, 119; in cotton dressings, 234; 
making of, 146-147 ; marine, 155 ; 
medicated, 156; mottled, 156; 
perfumed, 155 ; petroleum products 
in, 153 ; reaction with bleaching 
powder, 247; rosin, 152; scouring, 
156 ; sodium silicate in, 152 ; sodium 
resinate in, 152; soft, 119, 147; 
transparent, 155; unsaponified fat 
in, 148, 149; water in, 149-150 

Soap wort, 160 

Soda, baking, see sodium bicarbonate; 
caustic, see sodium hydroxide; 
washing, see sodium carbonate 

Soda crackers, 275 

Sodium, 20, 26, 84, 87, 92, 101 

Sodium bicarbonate, 35-37, 88, 92 

Sodium bisulphate, 88 

Sodium bisulphite, 247,250, 251,259,260 

Sodium jS-naphtholate, 262 

Sodium carbonate, 36 ; in commercial 
soaps, 151, 156, 157; use in water- 
softening, 124—126 

Sodium chloride, 257 ; electrolysis of, 
1 01 ; preparation from sodium and 
hydrochloric acid, 84; reaction 
with silver nitrate, 6, 27, 31, 35; 
use in dyeing, 257; use in soap- 
making, 147 ; use in washing dyed 
cottons, 257 

Sodium ferrocyanide, 261 

Sodium hydrosulphite, 259, 260 

Sodium hydroxide, 92, 93, 101 ; elec- 
trolysis of, 101 

Sodium hypochlorite, 243, 247-248 



Sodium hyposulphite, 247 

Sodium perborate, 249 

Sodium peroxide, 249 

Sodium phosphate, 89, 227 

Sodium resinate, 152 

Sodium silicate, in soaps, 152; use in 
silk- weighting, 227 

Sodium sulphate, 117, 124, 257, 265 

Sodium sulphide, 259 

Sodium thiosulphate, 247 

Solution, by chemical action, 100; 
colloidal, 201-203; simple, 100; with 
and without ionization, 100 

Soot, 60, 76 

Souring in bleaching, 247 

Spectroscope, 73 

Spinach, 212, 273, 279 

Spirits, methylated, 67 ; of hartshorn, 128 

Squashes, 272, 278 

Starch, 166, 168, 171, 172, 177-179, 
209, 234, 235, 277; animal, see 
glycogen; arrowroot, 273 ; corn, 273, 
277; forms of granules, 178; iodine, 
test for, 171, 178; in cotton dress- 
ings, 234, 235; soluble, 179 

Steapsin, 144, 204 

Stearin, see tristearin 

"Stearin," commercial, 76 

Steel, 109 

Stove polish, 1 10 

Stoving, 251 

Substances, 9, 20 

Sucrase, 175, 176, 204 

Sucrose, 168, 175; in honey, 213 

Suet, 285 

Suffixes, signification of, -ate, 25 ; -ic, 
39; -ide, 25; -ite, 39; -ous, 39 

Sugar (cane-sugar), see also sucrose ; 
caramelization of, 181; decomposi- 
tion of, 12 ; elements of, 22 ; inversion 
of, 174; use in silk- weighting, 227 

Sugars, 166, 168; barley, 181; cane, 
see sucrose and sugar; fruit, see 
fructose ; grape, see glucose ; in- 
vert, 174; malt, see maltose; milk, 
see lactose 

Suint, 220 

Sulphur, 16, 19, 20, 26, 27, 249, 250; 
dyes, 259; in proteins, 184, 191; 
tarnishing of silver by, 106 ; use in 
bleaching, 251 

Sulphur dioxide, 250, 251 



INDEX 



307 



Sumac, 264, 265 
Symbols, 26, 29, 33 
Syrup, see sirup 

Taffy, 181 

Talc, 234 

Tallow, 75, 139, 141, 150, 155 

Tannins, 225, 264-266 

Tapioca, 177, 274, 275, 277, 287 

Tarnish of metals, 105-109 

Tartar, cream of, see potassium bi- 
tartrate 

Tartar emetic, 265 

Tea, 287 

Temperature, 51, 52; ignition, 53 

Textiles, chemistry of, 229—266 

Thermometers, 52 

Thorium, 79 

Tin, use in silk- weighting, 227, 228; 
a constituent of bronze, 106; as a 
protective coating for iron, 1 1 1 

Tinware, in, 112 

Toast, 275 

Tomatoes, 210, 272, 278 

Tongue, 213, 281 

Triolein, 140, 141 

Tripalmitin, 139, 140 

Tristearin, 139 

Trout, 215, 283 

Tryptophane, 184, 213 

Tungsten filaments, 80-81 

Turkey, 281 

Turkey red, 256, 264 

Turmeric, 256 

Turnips, 209, 272, 279 

Turpentine, 160 

Tyrosine, 213 

Ultramarine, 252, 253 

Uranium, 31 

Urea, 182, 194, 195, 197 

Valence, 87 

Vaseline, 66, no 

Vat dyes, 259 

Veal, 214, 215, 281, 282, 286 

Vegetables, 198, 200, 207-212, 272, 

273, 278, 279 
Venetian red, 107 
Vermicelli, 274 
Viscose, 239, 240 
Vitellin, 184 



Walnuts, 210, 276, 279, 287 

Water, electrolysis of, 12, 13, 30; ele- 
ments of, 22; hard, 121-126; in 
soaps, 149, 150; in foods, 162-163; 
in wool, 222 ; production in com- 
bustion, 8, 46-47 ; production from 
its elements, 13, 24, 30; softening 
of, 124 

Water glass, see sodium silicate 

Watermelons, 268, 271, 278 

Wax, bees', 76, 138; Carnauba, 138; 
cotton, 230; flax, 237; in cotton 
dressings, 234; paraffin, 66, 76, 
no, 133; spermaceti, 76 

Weights and measures, metric system 
of, 288-296 

Weights of one cupful of food materials, 
287 

Welsbach gas mantles, 79 

Wheat and wheat products, 274, 279 

Whey, 213, 215, 284 

Whitefish, 283 

Whiting, 107, 234 

Wine, 5 

Wood, 41, 59, 60—62, 180 

Wood-pulp, 229, 238 

Wool, 218-223, 241, 251, 259, 261; 
action of alkalies on, 222, 223; 
bleaching of, 251; carbonizing of, 
221; dyeing of, 259, 265; felting 
of, 219; factors influencing quality 
of, 219-220; grease, 220; hygro- 
scopicity of, 221 ; raw, 220; scouring 
of, 220; separation from cotton, 
241; structure of, 219; test for 
sulphur in, 191 ; treatment of, to 
prevent shrinking, 246 

Xanthoproteic test, 186 

Yeast, fermentation by, 5, 134, 175 

Zein, 184 

Zinc as a protective coating for iron, 

in; tarnish of, 105 ; a constituent 

of brass, 106 
Zinc chloride, 232, 234 
Zinc oxide, 243 
Zwieback, 275 
Zymase, 175 



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THE MORE IMPORTANT ELEMENTS 
With their Symbols and Approximate Atomic Weights 



Name of Element 


Symbol 


Atomic 
Weight 


Name of Element 


Symbol 


Atomic 
Weight 


Aluminium . . 


Al 


27 


Magnesium . . 


Mg 


24-3 


Antimony . 




Sb 


120 


Manganese . . 


Mn 


55 


Arsenic . 






As 


75 


Mercury . . 


Hg 


200.6 


Boron . 






B 


11 


Nitrogen . . 


N 


14 


Calcium 






Ca 


40 


Oxygen . . . 





16 


Carbon . 






C 


12 


Phosphorus 


P 


3i 


Chlorine 






CI 


35-5 


Potassium . . 


K 


39 


Copper . 






Cu 


63.6 


Silicon . . . 


Si 


28.3 


Gold . 






Au 


197 


Silver . . . 


Ag 


108 


Hydrogen 






H 


1 


Sodium . . . 


Na 


23 


Iodine . 






I 


127 


Sulphur . . . 


S 


32 


Iron . . 






Fe 


56 


Tin ... . 


Sn 


119 


Lead 






Pb 


207 


Zinc .... 


Zn 


65-4 



